SuzukiSavage.com /cgi-bin/YaBB.pl General Category >> Rubber Side Down! >> Wiseco Flat Top Piston - Installation & Test /cgi-bin/YaBB.pl?num=1613022271 Message started by DragBikeMike on 02/10/21 at 21:44:31

Title: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 02/10/21 at 21:44:31 In June of 2020, Dave got in touch with me and asked if I would like to collaborate with him and Lancer on a new flat-top piston.  A flat-top piston with increased compression height will provide a nice tight-quench area, which improves combustion and increases compression.  I had already built an engine with tight-quench and it ran really well, but it required some machining and the installation of a special jack bolt to take up excessive cam chain slack.  A special piston with increases compression height would eliminate the need for machining, and it would allow the use of the stock cam chain configuration.   This old post provides the details of the original Tight-Quench engine and the concept behind the approach. http://suzukisavage.com/cgi-bin/YaBB.pl?num=1567201633

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 02/10/21 at 21:45:36 The special flat-top piston with higher compression height would make a tight quench engine a piece of cake.  No machining, no cam chain issues, I was all in. I got in touch with Lancer and provided this sketch.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 02/10/21 at 21:46:22 Lancer got together with Alan Pizzino at Wiseco and a few months later we had a prototype in hand.  The Wiseco Flat-Top project was good-to-go.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 02/10/21 at 21:47:53 The two big changes on the new piston are the increased compression height (1.250” vs 1.099”) and the dish machined into the top of the piston. Here you can see the difference in compression height between the stock piston and the new Wiseco flat-top.  Also note that the rings are situated higher.  This piston won’t tolerate any sort of ridge in the cylinder.  I wouldn’t recommend installation in a high-mileage cylinder, and it’s best to use a rigid hone to clean up the bore.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 02/10/21 at 21:48:48 This shows the dish in the top of the piston.  I measured it at .074” deep.  Without this dish, the compression ratio gets a bit too high for pump gasoline.  For the dish, I was looking for a trench cut rather than a spherical cut.  The trench cut would preserve more quench area and increase the volume of the dish.  We’ll find out how it works with the spherical cut.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 02/10/21 at 21:49:38 Here you can see how the spherical cut eliminates some of the quench area.  That’s a .020” pin gage between the tool bit and the piston.  The quench area runs all the way to the edge of the valve relief in the top of the piston.  So, the spherical cut runs through a little over one-half of the quench area.  If I set it up with .040” clearance, it will have .040” at the outer edge and gradually transition to .060” at the edge of the valve relief.  Which is better, .040” all the way or .040” about half-way gradually increasing to .060”?  The gradually increasing configuration might work like a nozzle (possibly good) or it might diminish the desired turbulence (not good).  Again, we shall find out.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 02/10/21 at 21:50:41 I was also hoping that Wiseco would extend the skirt to match the stock piston.  I felt it would add stability and allow the piston to run quieter.  I’m no piston engineer so I must defer to Wiseco.  I’m sure their engineering staff looked at all aspects of the design.  Here you can see how much longer the stock skirt is compared to the Wiseco skirt.  The Wiseco pop-top also has a short skirt.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 02/10/21 at 21:51:27 This shows the differences in the skirt configuration.  Stock at the top, pop-top on the right, flat-top on the left.  It’s pretty evident that the stock piston, with it’s longer & fuller skirt, will provide the most stability.  The cast material also needs less running clearance.  The stocker should be the quietest of the three, while the pop-top should make the most noise.  I’ve been running the pop-top and it’s only a little noisier than stock.  Hard to guess how noisy the flat-top will be.  It has more skirt than the pop-top, but the increased compression height might add to the rocking and thrust loads.  Another burning question that needs an answer.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 02/10/21 at 21:52:07 Piston assemblies are part of the reciprocating mass.  Their weight is taken into consideration when the crankshaft is balanced.  Change the weight of the piston assembly by a significant amount and you end up with a shaker.  The stock piston assembly (piston, pin, rings & clips) weighs in at about 499 to 507 grams (I’ve weighed several of them).  The 94mm Wiseco pop-top weighs in at 455 grams and it shakes noticeably more than the stock piston.  It takes a toll when you run on the freeway for an extended period.  The 97mm Wiseco pop-top weighs in at 496 grams.  It runs a lot smoother than the 94mm pop-top.  This new Wiseco flat-top weighs in at 512 grams.  It will be interesting to see where it falls on the seismic scale.  The nice thing here is it would be simple to reduce its weight to a value closer to stock.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 02/10/21 at 21:52:50 Here you see the wrist pins for the three different pistons.  Pop-top on left, flat-top center, stock on right.  The wrist pin for the flat-top is heavy wall.  Looks to me like the inside diameter could be ground a bit to bring the weight down a few grams.  I’ll keep that in mind if this thing turns out to be a shaker.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 02/10/21 at 21:53:38 To get started, it seemed like a good idea to see where the deck height was.  I intended to use a .021” copper base gasket so I did a rough assembly with and old copper base gasket, no rings, and no wrist pin clips.  Things looked great.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 02/10/21 at 21:54:20 In contrast, here’s how the deck height looks on the stocker.  No quench on this one.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 02/10/21 at 21:54:56 No quench on the pop-top either.  Note the orientation arrow.  It faces the exhaust side.  The new flat-top doesn’t have one of those arrows.  More later.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 02/10/21 at 21:55:32 To accurately measure the quench clearance, use lead wire (sort of like using plasti-gage).

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 02/10/21 at 21:56:10 Place the lead wire on top of the piston.  A little grease helps to keep the wire in the correct location.  My lead wire is only about .030” diameter so I stack it up on feeler gages.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 02/10/21 at 21:57:02 Install a used head gasket and the cylinder head.  Torque the head nuts.  Turn the engine through several rotations, then take the head off and measure the thickness of the lead wire.  In my case, the thickness of the lead wire and feeler.  I got .038”.  Pretty darned close to the target.  Good enough.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 02/10/21 at 21:58:01 Now that we know what the quench clearance is, we can calculate the deck height.  The compressed thickness of the head gasket is .028” so the deck must be .010” for a total of .038”. All we need now is the volume of the piston dish and valve reliefs.  Install an old top ring on the piston and position the piston down the bore a known amount.  Then seal around the top of the piston with grease.   A quick fill with the burette and a little math and you have the no bull volume.  It’s 6.6 cc.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 02/10/21 at 21:58:40 Armed with a bunch of data, we can go to the RB Racing website and use their calculator to see what the actual static compression ratio will be.  The magic number is 10.42:1.  That’s pretty high.  Hope the local refinery can keep me out of the detonation zone.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 02/10/21 at 21:59:33 After a few passes with a rigid hone to break the glaze and ensure there was no ridge, it was time to set ring gaps.  I’m generous with ring gaps ever since I cooked one of these high compression engines.  It’s air cooled, so it’s not such a bad idea to add a little extra gap.  I used Wiseco’s spec for “Blown Race Only” application (top ring .0065”per inch of bore, 2nd ring .0070” per inch of bore).  That works out to .024” for the top ring and .026” for the second ring.  The top ring only had .018” gap so I had to file it.  The 2nd ring already had .028” gap right out of the box, so I left it as-is. Some abrasive paper over a machinist’s scale works good.  Hold the scale and abrasive paper in a machinist’s vice or something similar.  The top surface on the vice helps to keep the ring square as you dress the butt.  Work only one side and always move the ring away from you so you don’t chip the special coating on the ring.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 02/10/21 at 22:00:12 Make sure the ring is square in the bore when you check the gap.  The edges of the butt should be parallel.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 02/10/21 at 22:00:51 Wiseco specifies running clearance of .0025” for this piston.  The value is on the box that the piston comes in.  Unfortunately, my cylinder has been honed several times.  I had to live with a loose .003”.  I generally like to run forged pistons a bit on the loose side, but for this test I wanted to try and follow the specs provided.  I’m sure it won’t hurt performance, but it might make a bit more mechanical noise.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 02/10/21 at 22:01:38 I mentioned earlier that the piston does not have an orientation arrow.  You must measure the valve reliefs to determine which side is for the intake valves and which side is for the exhaust valves.  The intake relief is 63mm wide.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 02/10/21 at 22:02:13 And the exhaust relief is 59 mm wide.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 02/10/21 at 22:03:44 This piston runs very close to the head, about .150” closer than the stock piston.  It is mandatory that valve-to-piston clearance be checked.  Web specifies a minimum clearance of .080” for the exhaust valves and .050” for the intakes.  Other experts are more conservative, .100” for the exhaust and .080” for intake.   I am running the Web 340b cam in this engine.  It has more TDC lift than any of the other readily available cams (.143” Int/.092” Exh).  I found that the combination is unforgiving.  To meet the minimum clearance specs the cam timing had to be exact.  The slightest bit of advance or retard resulted in the clearance dropping below minimum.  Advancing resulted in the intake valve getting too close, retarding resulted in the exhaust valve getting too close.  It had to be spot on to meet the minimum clearance spec.  No playing around with cam timing on this combination.  I ended up with .06” on the intake and .08” on the exhaust. You can check the valve to piston clearance with modeling clay.  Install the piston and cylinder with the correct thickness base gasket.  Degrease the top of the piston and apply modeling clay in way of each valve.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 02/10/21 at 22:04:23 Then apply a generous layer of grease on the valves and quench area on the head.  The grease keeps the clay from sticking to the valves and cylinder head.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 02/10/21 at 22:06:44 Now install the forward cam chain guide and cylinder head with a used head gasket.  Properly torque all the head nuts.  Install the cam, cam sprocket, cam chain, rear chain guide and tensioner.  Set the cam timing.  Make sure the factory marks line up perfectly.   Rotate the engine through several turns and make sure the factory timing marks align perfectly each time you stop at top dead center. Once you are confident that the cam timing is just right, install the head cover with rocker arms.  Adjust all four valves to .004”.  Now carefully rotate the engine in the normal direction of rotation (clockwise viewed from the right side).  If you feel anything that might be contact between valve and piston, STOP.  Figure out what’s wrong before you continue to rotate the engine.  If it rotates normally with no indication of contact, continue to rotate at least four revolutions.  Then remove the cylinder head to inspect the clay impressions. Use a small knife to cut through the center of the clay impressions.  Dip the blade in water to keep the clay from sticking.  Use light pressure so as not to mar the top of the piston. Here is what the intake impression looked like after cutting through the clay.  It gives a clear picture of how close the valve comes to the piston.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 02/10/21 at 22:07:25 This is the exhaust impression.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 02/10/21 at 22:08:06 A small drill bit with a short section of plastic spray tube from an aerosol product works good for measuring the thickness of the clay.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 02/10/21 at 22:08:50 Check the distance between the face of the valve and the piston.  It should be at least .05” for the intake valves and .08” for the exhaust.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 02/10/21 at 22:09:28 You also want to check the radial clearance between the valve OD and the piston relief.  I don’t have a spec but .05” seems reasonable to me.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 02/10/21 at 22:10:12 All the clearances had been checked.  The compression ratio had been verified.  Time to put it together and see how it runs.  I followed standard assembly procedures.  Once the engine was back in the frame, I filled the crankcase with Castrol 20W-50 V-Twin motorcycle oil.  Then pre-lubed the top end by filling the reservoir (trough) below the cam lobes with an oil can.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 02/10/21 at 22:10:50 It was ready to crank.  I like to see pressure build on my oil pressure gage before I fire up an engine for the first time.  So, I always crank my engine with the spark plug removed until I see the gage start to register some oil pressure.  It’s a good time to take the initial compression reading.  It pumped about 225 psi.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 02/10/21 at 22:15:20 It fired up and ran good.  The idle was a little cobby for a while but eventually it smoothed out.  It felt frisky, was quiet, and the vibration levels were low.  No leaks.   I proceeded to break in the new piston.  I checked fuel mileage three times during the break-in.  I was impressed.  On the first mileage check it got 73 mpg.  That seemed like it was too much.  Thought I might have made a mistake.  The second check it got 65 mpg.  Less but still better than I had ever observed on the Savage.  Third check it got 69 mpg. Man, this thing is efficient.   After it passed the 400-mile mark, I took it for a long ride (for me). About one-third of the ride  was haulin freight on the freeway, about one-third on 50 mph country roads, and one-third on 40 mph surface streets. It went 114 miles on 1.48 gallons of fuel.  There was nothing gentle about this ride.  It wasn’t an attempt to set a fuel mileage record.  It got a whopping 77 mpg.   After it passed the 500-mile mark, I did another long run, only this time I rode it full bore.  Plenty of WOT.  Lot’s of freeway.  After 102 miles it had sipped 1.42 gallons of fuel.  The little 94mm took a lickin, kept on tickin, and got 72 mpg under some pretty aggressive riding.  That made a believer out of me.  It’s not an anomaly.  Five fuel mileage checks and every one showed fuel economy at 65 mpg or better.  The average fuel economy works out to 71.2 mpg.  I guess that gradually-increasing quench zone gets the job done.  My concern over the spherical dish has been put to rest.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 02/10/21 at 22:16:23 All through the break-in and subsequent testing, the oil temperature and cylinder head temperature (CHT) have remained low.  It’s hard to compare the temperatures to my other engines because the ambient temp has been unusually low.   I took it on my standard heat run.  It’s a 50-mile run up through the Koolau mountains over to the Windward side of the island.  The run has long uphill grades at freeway speed.  The tach spends most of its time at 4500 rpm and never drops below 4000 rpm.  Ambient temperature was 75°F.  The oil temp never exceeded 200°F and the CHT never exceeded 296°F.   On this particular heat-run course, I’ve seen the 97mm Big-Bore reach oil temp as high as 230°F and CHT as high as 360°F.  The 94mm Pop-Top ran 242°F oil temp and 343°F CHT.  I don’t think the Wiseco Flat-Top is going to have any overheating issues.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 02/10/21 at 22:18:06 How’s the power?  It felt powerful, with a willingness to rev fast, but the seat-o-da-pants dyno doesn’t cut it.   In preparation for this project, I did some baseline tests on the 94mm Wiseco Pop-Top.  The intent of the project was to see how the two pistons compare.  So, the two setups would be identical except for the pistons.  Same crankcase, same cylinder, same head, same cam, same carb, same air filter, same exhaust, same ignition, same flywheel, same gearing, etc.  I even used the same old spark plug.  The only thing different was the piston. The benchmark would be a 3rd gear pull from 4K to 7K at my standard test location.  The 94mm Wiseco Pop-Top engine did that pull in 6.68 seconds.  That’s the benchmark. The Flat-Top engine did that 3rd gear pull in 5.65 seconds.  That’s impressive.  It’s over a full second faster than the Pop-Top piston.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 02/10/21 at 22:20:00 While I was building the Flat-Top engine I was playing with the 97mm Big Bore.  I did a bunch of 3rd gear pulls with the LCGP HiFlow muffler and then tried some pulls in 5th gear.  Starting the 5th gear run at 3.5K and ending at 5.5K accelerates from 55 mph to 85 mph (like passing a big rig on a country road).  I felt that would simulate real world conditions.  So, I did some 5th gear pulls on the Flat-Top engine too.  Unfortunately, I came up with this 5th gear test after I had pulled the 94mm engine out of the frame, so I don’t have any 5th gear data on the 94mm Pop-Top. The 97mm Big-Bore does the 3rd gear pull in 5.72 seconds.  As mentioned previously, the Flat-Top does the 3rd gear pull in 5.65 seconds. The 97mm Big-Bore does the 5th gear pull in 6.56 seconds.  The 94mm Flat-Top does it in 6.53 seconds. Wow!  The 97mm Flat-Top is just as fast as the 97mm Big-Bore, even in top gear from as low as 3500 rpm.  This is one speedy little piston.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 02/10/21 at 22:21:12 During the break-in, as I started to ride it a little harder, it was evident that there is more mechanical noise.  The piston clearly rattles a bit.  I can’t help but wonder if the skirt were a little longer would it reduce that noise?  I don’t know what effect that will have on longevity.  It’s not obnoxious but it is unsettling.  As I mentioned earlier, forged pistons make more noise than cast pistons, and I have a bit more clearance than Wiseco recommends.  At this point, I’m not too concerned about the noise. At a little over 500 miles, I checked valve clearance, inspected the spark plug, inspected the piston with a flexible camera, checked compression, and checked my breather can for oil.  The valves were all .005”.  The spark plug was pretty dark and there was no evidence of detonation.  It’s getting enough fuel.  The piston looks great (what I can see of it), no sand blasting, pitting or missing chunks.  It seems to be doing fine on 92 octane.  Compression has bumped up to 230 psi.  The breather can was dry, no indication of excessive blow-by. Here’s a look at the plug.  My best acceleration times were with a 230 main jet and the air/fuel meter was in the mid 12s.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 02/10/21 at 22:23:28 So, how does the new Wiseco Flat-Top work?  Great. It’s a simple installation that can be accomplished with routine tools (no machining, welding, etc.)  It requires good attention to detail and ALL clearances MUST be checked, but you don’t need much more than a standard set of tools, a good cylinder hone, a set of feeler gages, and some modeling clay to get the job done. It bumps the compression ratio up over two points (8.2:1 to 10.4:1). It provides good, tight quench for improved turbulence and combustion.  It’s clearly more efficient. It will work with 92 octane pump gas.  I had no issues with detonation.  I can’t guarantee this with other cams, but it worked fine with the 340b. It runs cool. It runs smooth.  Vibration levels seem on par with the stock piston.  It is much smoother than the 94mm Wiseco pop-top. It measurably improves performance and economy.  The improvements are dramatic.  It’s faster than the 94mm Pop-Top, and just as fast as the 97mm Big-Bore.  Fuel economy is off the hook.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 02/10/21 at 22:25:25 That pretty much sums it up.  I want to give a BIG shoutout to Dave & Lancer for collaborating on the project.  Dave cross checked my sketches and calculations.  Lancer worked out the details with Wiseco, and he took the financial plunge and associated risk required to do the special order.   I hope you find this report informative.  As usual, I welcome your questions and comments.  I will continue to log miles on the new Flat-Top.  If something interesting comes up, I will update this report. Mask up.  Stay safe.   Stay well. Mike

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by Gary_in_NJ on 02/11/21 at 07:27:52 Wow, 230 psi. That's a lot of squeeze.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by Dave on 02/11/21 at 16:31:53 Great write up and results.....as usual! It is nice that you were able to get a significant power increase by improving efficiency - rather than just going bigger.  More power and increased mpg - that is not often achievable. It will be interesting to see how long you leave your bike together this time........have you found the power and performance you are looking for?  Or - are you already scheming on the 97mm flat top piston? ;)

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by Gary_in_NJ on 02/11/21 at 16:47:15 At some point I will probably swap in some new cams and do some porting to the head. This piston is a great “plug-n-play” solution for a performance gain.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by ohiomoto on 02/11/21 at 19:38:26 75737C00020501310 wrote: Lancer got together with Alan Pizzino at Wiseco ... ------------ LOL, I used to race with that guy!

Title: Re: Wiseco Flat Top Piston - Installation & Te Post by ohiomoto on 02/11/21 at 19:48:07 14121D61636460500 wrote: It fired up and ran good.  The idle was a little cobby for a while but eventually it smoothed out.  It felt frisky, was quiet, and the vibration levels were low.  No leaks.   I proceeded to break in the new piston.  I checked fuel mileage three times during the break-in.  I was impressed.  On the first mileage check it got 73 mpg.  That seemed like it was too much.  Thought I might have made a mistake.  The second check it got 65 mpg.  Less but still better than I had ever observed on the Savage.  Third check it got 69 mpg. Man, this thing is efficient.   After it passed the 400-mile mark, I took it for a long ride (for me). About one-third of the ride  was haulin freight on the freeway, about one-third on 50 mph country roads, and one-third on 40 mph surface streets. It went 114 miles on 1.48 gallons of fuel.  There was nothing gentle about this ride.  It wasn’t an attempt to set a fuel mileage record.  It got a whopping 77 mpg.   After it passed the 500-mile mark, I did another long run, only this time I rode it full bore.  Plenty of WOT.  Lot’s of freeway.  After 102 miles it had sipped 1.42 gallons of fuel.  The little 94mm took a lickin, kept on tickin, and got 72 mpg under some pretty aggressive riding.  That made a believer out of me.  It’s not an anomaly.  Five fuel mileage checks and every one showed fuel economy at 65 mpg or better.  The average fuel economy works out to 71.2 mpg.  I guess that gradually-increasing quench zone gets the job done.  My concern over the spherical dish has been put to rest. --------- Those are some astounding numbers.  I'm big guy but I'm lucky to get much over 50-52 mpg. What would you expect from a stock motor under those same conditions?

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by Armen on 02/11/21 at 20:20:38 Wow! Great work! Great reporting and documentation! Thanks for sharing!!!!

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 02/12/21 at 02:24:24 You are right Gary, 230 psi is kinda high.  The first one I built (using the stock cast piston) pumped 245 psi.  I was always nervous about that one.  I actually set that one up with .060" quench in an effort to keep the cranking pressure down.  This forged piston, with a dish to reduce compression ratio, allows bringing the quench down to .040".  That's the target number.  Detonation does not seem to be a problem.  The tighter quench is actually supposed to reduce the potential for detonation.  So far, it seems to be doing that.  It's a very crisp running engine. Dave, I will never find the power and performance I am looking for.  My LS650 is a laboratory on two wheels.  The only reason I have it is to experiment and share.  If I ever run out of things to tinker with, it will be time to get rid of it.  Regarding a flat-top 97mm with tight quench, you read my mind.  I have to come up with a stronger clutch first. Ohio, I usually don't care too much about fuel mileage, so I don't have much data on the stock engine.  I can say that the few times I checked mileage on the stock setup it was in the 50s.  I started looking at it a little closer when I was working on the muffler comparison.  I knew one of the benefits of a free flowing exhaust is supposed to be increased fuel economy.  Same goes for high compression.  So, I was compelled to check it.  It was such a dramatic improvement I had to keep digging into it. Armen, it was my pleasure.  Are you moved in yet?

Title: Re: Wiseco Flat Top Piston - Installation & Te Post by LANCER on 03/15/21 at 08:33:55 New order of flat top pistons is due about the end of the month, 6 94's and 4 97's this time. Taking preorders now if anyone is interested.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by Armen on 03/15/21 at 19:34:59 Ooooooh I have a 97mm barrel that I bought from Dave. I think he had it Nikasil coated. If your 97mm piston and this cylinder can be friends, I'm in! thanks

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by LANCER on 03/16/21 at 04:29:08 6B58474F442A0 wrote: Ooooooh I have a 97mm barrel that I bought from Dave. I think he had it Nikasil coated. If your 97mm piston and this cylinder can be friends, I'm in! thanks Only getting 4 of the 97’s so process payment to hold one for you.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by Armen on 03/16/21 at 06:08:53 Sending today.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 04/26/21 at 19:10:19 I had logged 2250 trouble-free miles on the Wiseco Flat-top and it was time to start my next project.  I figured I would update this post to let you all know how the new Wiseco is holding up.   The piston has performed admirably. Power is outstanding.  I’ve managed to squeeze a bit more steam out of it with a PWK40 carburetor.  It’s killer fast, everywhere. Fuel mileage continues to run in the low 70 mpg range.  I almost never get less than 70 mpg (it’s usually around 72 to 73 mpg). The subtle piston rattle has remained about the same.  Doesn’t bother me in the least.  On 92 octane pump gas, there have been no audible detonation issues.   The engine operating temps are still well below what I observed with the 94mm pop-top and the 97mm pop-top.  The temps are also well below what I have observed with a completely stock 8.5:1 compression LS650.  This flat-top piston is much more efficient.  It’s converting more thermal energy to work instead of rejecting the heat through the cylinder & head.  The flat-top engine runs a good 20°F cooler on surface streets and about 40°F cooler on the freeway. A quick compression check prior to teardown showed the Flat-Top is pumpin a solid 235 psi.  Things are still fresh as a daisy under the hood. Let’s have a look at the inside of the engine.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 04/26/21 at 19:11:42 The handy-dandy cylinder stud remover made disassembly a breeze.  I’m lovin this tool.  Don’t even have to remove the battery.  R&R cylinder head and cylinder in no time flat.  Projects galore with this little jewel.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 04/26/21 at 19:12:25 The combustion chamber looked primo.  Very little carbon accumulation and absolutely no evidence of contact between the piston and head (that’s with many trips past 7500 rpm).  No tell-tale signs of detonation.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 04/26/21 at 19:13:14 The top of the piston also had very little carbon accumulation.  It looked great.  Again, no signs of contact or detonation.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 04/26/21 at 19:14:05 With the cylinder removed, you can see that the noise really isn’t an issue.  The piston looked brand new.  The rattle is just amplified by the cooling fins on the cylinder.  There’s no indication of any sort of distress.  Sweet!

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 04/26/21 at 19:16:35 I think the Wiseco Flat-Top piston is a complete success.  It looks like it’s a great modification that will improve performance and efficiency.  It also looks like it will provide reliable service. Now its time to move forward with the next project.  How’s a completely stock LS650 sound?  We’re talkin 55 to 85 mph in 22.43 seconds.  Seriously?  You bet.  ;)

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by ohiomoto on 04/26/21 at 20:01:12 42444B37353236060 wrote: Now its time to move forward with the next project.  How’s a completely stock LS650 sound?  We’re talkin 55 to 85 mph in 22.43 seconds.  Seriously?  You bet.  ;) ---------------- That's 7 seconds to get to 80 and 15.43 to get from 80 to 85 mph.   :)

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 06/07/22 at 01:29:34 My Evolution of a HotRod project hit a snag.  The transmission failed.  The engine had evolved into a 694cc fire breathing beast.  It had the new 97mm Wiseco Flat-Top piston and it was running good.  Too good.  Fifth gear failed.  The teeth gave up (severe pitting) and spread debris throughout the crankcase. I was lookin at a lot of work.  The crank needed to be straightened, all the bearings were suspect, the cylinder was toast, and a beefed-up transmission was in order. I wanted to keep my test program going.  My to-do list had some things that looked interesting, and lots of things needed a long-term test to prove they would last.      -DR650 cam durability      -Cagiva valve adjuster durability      -Shortened valve guide durability      -Epoxied intake port life expectancy      -Improved breather system with Hayden KrankVent      -High-flow muffler with larger 1.75” baffle      -Knock-off PWK carb durability and stability      -Wiseco flat-top piston durabilty      -Floating cam chain tensioner wear trend & durability      -Ignition timing optimization      -13 plate clutch durability      -Sneezy clutch release cam durability       Since the big engine would be down for a while, I needed a replacement.  Time to put the 2nd string in.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 06/07/22 at 01:30:57 It looked like a good opportunity to log a bunch more miles on the 94mm Wiseco Flat-Top piston.  To keep things moving forward, I assembled my spare engine. I did a good visual inspection of the spare engine’s accessible transmission gears.  There was no visible pitting or distress.  Runout on the ends of the crankshaft was under .002” TIR.   Bearing free play was tighter than the bearings in the failed engine.  It looked like I was starting out with a decent lower end.  I intend to keep a close eye on it.  That magnetic drain plug will be scrutinized at every oil change.  No more runnin the guts out of it with chunks of gear teeth circulating in the oil. The 94mm cylinder was in perfect condition.  I washed up the cylinder and piston assembly and installed them on the spare crankcase.  Didn’t even change the rings.  They only had 2250 miles on them (almost new).  Re-using piston rings is not something I typically do, but it didn’t seem egregious.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 06/07/22 at 01:32:13 The Web 340b cam had to go.  It was pitted.  I had used the 340b in my original Tight Quench Engine, the Wiseco 94mm Pop-Top engine, and the first iteration of this Wiseco 94mm Flat-Top engine.  The 340b only 7272 miles on it.  What a shame.  Not sure what caused the pitting.  Poor weld, heavy springs, debris, who knows?

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 06/07/22 at 01:32:52 I needed a cam to keep the program goin, so I resorted to the trusty old DR650 cam.  It had about 11,463 miles on it.  Still looked pretty good.  It had some very small pits that were only visible at 5X magnification, but nothing like the craters in the Web 340b.  The new test mule would get the DR650 cam.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 06/07/22 at 01:33:40 I try to keep my cams and rockers in matched sets.  The rockers that I run with the DR650 cam looked perfect, so those went into the sausage grinder too.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 06/07/22 at 01:35:11 Because I would be running my Stage II head, I was able to install the special Cagiva valve adjusters.  The Cagiva adjusters don’t fit the Stage III head, but they do fit the Stage II head.  Might as well give them a long-term test to see how the adjusters and valve tips hold up. These special adjusters have a larger footprint and a tighter spherical radius.  They allow for higher lift without edge loading.  The intent is to prevent edge chipping, a problem I experienced with the stock adjusters.   Unfortunately, I haven’t been keeping track of the mileage on these components.  I estimate they currently have about 500 miles on them.  The DR cam doesn’t have enough lift to warrant the special adjusters, but they look to me like they will be a lot easier on the valve stems.  A long-term test seemed like a good idea.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 06/07/22 at 01:35:55 I’m basically lazy.  The Stage II head was set up with the heavy-duty RD spring kit and DR650 valves.  The DR650 cam does not require the heavy-duty long-travel springs, but if I wanted to convert back to stock springs, I would have to replace all four valves.  No thanks.  I’m not goin through all that hullabaloo.  I decided to leave the head as-is.  It was a good opportunity to see how the DR650 cam handles the higher spring pressure.  The RD springs exert about 28% more force than the stockers.  That means a lot more pressure on the cam lobe.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 06/07/22 at 01:36:59 Since I was switching the cam from the Web 340b to the DR650, I did clay checks to verify piston-to-valve clearance.  I’m pretty sure this was a waste of time since the DR 650 cam has significantly less TDC lift than the Web 340b, but I wasn’t takin any chances.  The Flat-Top piston runs mighty close to the head. Things looked great in the clearance department.  With .040” quench clearance and cam timing set to the factory marks, the valves stayed well away from the piston.  The DR650 cam was not gonna present any sort of clearance problem with the Wiseco Flat-Top.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 06/07/22 at 01:38:29 I’ve been wanting to revisit the cam chain tensioner.  A few guys are running tensioners without the pawl.  Sort of a free-floating setup.  Most are incorporating a hard-stop to restrict backward movement of the plunger to about .04” to .06”.  I ran a setup like that for a little while. If the valve-to-piston clearance is on the ragged edge (like on the 97mm Flat-Top I built), then I’m not a fan of any play in the cam drive.  But this 94mm Flat-Top engine, with the DR cam and 33mm intake valves, had ample valve-to-piston clearance.  It looked forgiving enough to permit some leeway.  A cam chain tensioner with a bit of back-travel seemed tolerable.  I just have to do periodic checks and adjustments.  Since I ALWAYS inspect the chain tensioner when I do a scheduled oil change, periodic checks won’t be a problem.  A bit of float will reduce some of the stress on the cam drive. I have an adjustment bolt on my cylinder head that allows me to adjust the arc of the rear chain guide.  That bolt, in conjunction with a floating tensioner, allows me to do periodic adjustments.  This is the setup for the adjustment bolt (which is just a 5/16-NF continuously threaded stud).

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 06/07/22 at 01:39:14 This is the pawl-free plunger (shown on top).

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 06/07/22 at 01:40:14 This is the modified tensioner.  The plunger goes hard at 10.5mm, so I set it to 12.0mm (cold).  That allows it to retract 1.5mm (.060”) as the engine heats up.  It should be very close to the hard-stop when the engine is at normal operating temperature.  When I change oil, I will check the extension, and adjust as necessary.  Just a simple turn of the adjusting screw will bring the extension right back to 12mm.  I intend to keep track of it and report periodically.  We can all get a better feel for how these floating tensioners behave.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 06/07/22 at 01:41:12 The stage II cylinder head has a modified intake port that utilizes epoxy to reshape the floor of the port.  That epoxy had a small crack that developed at the 8mm stud hole in the bottom of the port.  I expected the epoxy would give up over time, but I don’t have a good feel for just how long it will last.   The Stage II head had about 8500 miles on it.  I want to see how well these epoxy jobs hold up, so I left the crack as-is.   The epoxy is easy to remove and reapply, but that wouldn’t tell me much about durability.  Although a big chunk coming loose and running through the engine would be bad, I decided to take the risk and see what I could learn.  It’s easy to inspect, so why not just monitor and see how it goes.  You can just barely see the crack if you enlarge this photo.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 06/07/22 at 01:43:26 The big 97mm engine exhibited several problems when it failed.  In addition to the transmission failure (heavy pits in 5th gear), there was high vibration and audible noise, excessive crankshaft runout (about .004” TIR), and excessive main bearing play (about .0035”).  Since I didn’t have a good explanation for the runout and vibration issues, I opted to assemble the replacement engine with the stock flywheel.  I thought there could possibly be a connection between the super-light three-inch flywheel and the vibration issues.  There is almost no difference in performance, so I installed the big six-inch flywheel. I also couldn’t rule out detonation.  To be on the safe side, I retarded ignition timing 2°.  That would also give me an opportunity to see how the ignition timing affects driveability, operating temps, fuel economy, etc.   This little timing wheel rig along with a strobe light allows me to verify that the ignition timing is where I want it.  I was lookin for 2° BTDC at idle and 27° to 28° at 4000 rpm.  It’s a shame you can’t tweak it with the engine running.  Maybe someday I’ll work on that.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 06/07/22 at 01:44:00 Assembly was straight forward.  Cam timing was set at the factory marks.  I used a stock head gasket and ended up with .040” quench clearance.  Valves were adjusted to .004” intake and .005” exhaust.  The cam chain tensioner was set at 12mm extension which left 1.5mm back-travel (.060”).  The pseudo 40mm PWK carb was installed with a 145 main jet, 35 pilot jet, DGK needle (clip in 2nd groove), and 7.0 slide.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 06/07/22 at 01:48:07 The exhaust system got a mild upgrade.   I had built a new high-flow muffler with a larger baffle.  I ran it on the 97mm Flat-Top engine for a few miles.  Not long enough to see how it performed. The new baffle had a 1.75” ID with 288 perforations in lieu of the 1.65” ID baffle that had 216 perforations.  It reduced the restriction from 31.5” H2O to 26.5” H2O. This is the new baffle tube.  I think anything larger than this will start to increase restriction.  It wasn’t much louder than the 1.65” baffle.  It’s quiet.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 06/07/22 at 01:48:49 The muffler also got a new stainless-steel adapter to replace the painted carbon-steel adapter.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 06/07/22 at 01:49:23 The new adapter polished up nicely.  It was a good cosmetic improvement.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 06/07/22 at 01:50:05 The 97mm engine had evidence of fretting corrosion on the output shaft splines, so I made sure to coat the splines with moly-lube when I installed the drive pulley.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 06/07/22 at 01:50:46 Just the splines.  No moly-lube on the threads.  The threads get a few drops of Loctite 260 or 272 (the red stuff).

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 06/07/22 at 01:53:33 With the engine completely assembled and installed in the motorcycle, it was time to start the clock.  The odometer was reading 24,926 miles.  It’s probably a good time to tabulate exactly what I was getting ready to test. -Wiseco 94mm flat-top piston, .040” quench -94mm cylinder, stock height -Stage II head, 33mm intake valves, 28mm exhaust valves, 1.5” D-port, 56cc chamber -DR650 cam, stock late-model rocker arms, Cagiva valve adjusters -Floating cam chain tensioner, 12mm extension, .06” back-travel -Six-inch flywheel -Stock 5-speed transmission -Hybrid clutch, 13 plates, stock springs, Sneezy release cam -Knock-off PWK40 carb (actually 38mm) -K&N 3” x 5” cylindrical air filter -Mac 1.79” exhaust header pipe -LCGP 2.5” muffler with 1.75” ID baffle, 288 holes -Stock final drive pulleys The engine was close to the 94mm flat-top engine that I originally built in February of 2021.  The only significant changes were: -PWK carb -Big flywheel -DR650 cam -Floating cam chain tensioner -Larger baffle in muffler -Ignition timing retarded 2°

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 06/07/22 at 01:54:49 I topped it off with break-in oil and took it easy for about 220 miles.  It ran fine, nothing unusual, felt just like it did before.   I dumped the oil and refilled with Mobile 1 V-Twin 20W-50.  The magnetic drain plug was clean.  No metal chips.  Commence the endurance test.   The days of runnin the guts out of it are over.  My program will now focus on durability.  No more WOT pulls, over & over & over.  Just gonna ride it like a regular biker.  It will see normal service, lot’s of high-speed cruising, passing trucks and rubber-neckers, occasional WOT trips to 6500 rpm. The plan is to log at least 10,000 miles on the 94mm flat-top while I build the new 97mm four-speed engine package.  I’ll pick off items on the to-do list while I’m runnin the endurance test.  Since the flat-top piston makes such a big difference in fuel consumption, I plan to keep good records on that parameter.  Oil pressure, oil temperature, and cylinder head temperature (CHT) will be monitored, as well as oil consumption.  The oil will get changed at 3500-mile intervals.  Each time I change the oil I will inspect the cam chain tensioner and see what sort of wear to expect from the floating plunger setup.  Also, at each service interval I will check valve clearance and cranking pressure.   Every now and then I will take a peek at that crack in the intake port epoxy.  This should be interesting.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 06/07/22 at 01:57:04 First 3500 miles. It had great power.  Seemed just as healthy as it did before I started the Evolution of a HotRod project.  Audible noise and vibration were normal.  The new muffler was quiet and seemed to be making good power.  There was no discernable change that could be associated with the heavy flywheel, and power characteristics felt identical to the prior setup.  The two cams run about the same.  So do the carbs.  I really can’t feel any difference between the VM and the PWK. Oil pressure & temperature remained the same.  Usually about 8 psi and 200°F at 4000 rpm.  CHT was about the same or possibly just a bit hotter.  It ran about 280°F to 300°F.   Fuel consumption was a bit higher, even with the less restrictive muffler.  It was still getting excellent fuel economy, but it wasn’t deep into the 70 mpg zone.  It was averaging mid to high 60s, with an occasional 70 mpg ride.  Still stellar mileage, but not as good as it was before.  The increased fuel consumption could be related to the carburetor, flywheel, ignition timing, or the cam.  I’m gonna guess it’s the cam. Although the milder DR650 cam would generally be associated with improved fuel economy, this motorcycle has extremely low gearing which seems to favor the hotter 340b cam.  I think the hotter cam, with more overlap and TDC lift, compliments the gearing.  Its more efficient at the LS650’s high cruising rpm.  Just a guess on my part.  I suspect the retarded ignition timing didn’t help either. Oil consumption was up.  It used about 6 to 8 ounces every 1000 miles.  That was a significant change.  The first iteration of this engine didn’t seem to use much, if any, oil.  Now it needed oil every 1000 miles.  Not a big deal, but it was a change that I couldn’t explain.  Maybe re-using piston rings has something to do with it.  My guess would be the cast-iron oil scraper (2nd ring).  Maybe I should have installed a new set of rings.  However, I don’t consider 8 ounces every 1000 miles as anything to worry about. All went well.   The engine ran great.  On 4/26/22 the odometer was reading 28,654 miles.  Time to change the oil and do an inspection.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 06/07/22 at 01:57:43 I dumped the Mobil 1 and checked the magnetic plug.  No chunks, just ferrous sludge.  A good sign.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 06/07/22 at 01:58:35 The spark plug looked fine.  It had a little more color than I would like but nothin ugly was goin on.  I have no idea how many miles are on this plug.  You can see that it’s pretty old.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 06/07/22 at 01:59:13 Valve clearance was OK.  The intakes were .005” and the exhausts were at .006”.  No indication that the Cagiva adjusters, valve tips, or cam lobes were wearing rapidly.  I have never found a tight valve on the LS, they always gain clearance.  Never found any evidence of valve seat recession either.  I left the valves as-is.  I want to see where they are at the 7000 mile mark.  Note that the Cagiva adjusters use a square head instead of a slotted head.  I find they are a little easier to adjust.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 06/07/22 at 02:00:07 The cam chain tensioner looked fine.  It was at 12.5 mm, so it had only gained about 0.5 mm.  Rather than tweak it back to 12 mm I left it where it was.  Again, I want to see how it looks at 7000 miles.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 06/07/22 at 02:01:04 While I had the clutch cover off, I installed the new Sneezy clutch release cam.  It fit good and worked fine.  I’m sure it will last a long time.  I didn’t disassemble the clutch but there were no outward signs of wear or distress.  It seems to be hackin the mission.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 06/07/22 at 02:01:38 Cranking pressure was 225 psi.  Pretty much the same as it was on the original 94mm flat-top.  I was happy with that.  I guess the compression ring was holding its own.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 06/07/22 at 02:02:14 I wasn’t finding any evidence of detonation.  The plug looked fine and there was no audible noise or vibration issues.  I decided to throw in a couple of degrees of ignition advance.  I wanted to see if I could find a few more mpg.  The alternator cover had to come off to adjust the timing.  The alternator rotor looked great.  None of that ugly sludge and debris I found on the engine with the transmission failure.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 06/07/22 at 02:02:58 I moved the ignition pickup .102” to add 2° of advance.  Every .051” equals 1°.  When it’s all back together I double check with my little timing wheel and a strobe light.  I was lookin for 5° at idle, right on the factory spec.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 06/07/22 at 02:04:42 Everything looked good.  I reassembled the engine, installed a new oil filter, and filled it up with Mobile 1.  The ignition timing checked out good.  I need to keep my eyes and ears open for any signs of detonation or unusual vibration.   At 29,274 miles on the odometer, I tried a new breather system that’s a little more friendly to our environment.  It uses the Hayden KrankVent to pull a slight vacuum in the crankcase.  I previously tried the KrankVent but didn’t have much luck with it.  I wanted to try again.  It’s an interesting contraption that seems to have merit.  I will do a separate report that discusses the installation.   So far, it’s working good. I’m currently at 31,145 miles.  Next oil change will be due at 32,154 miles.  It’s running great.  Fuel consumption has improved a bit and I’m not hearing the dreaded spark knock.  It still uses about 6 to 8 ounces of oil every 1000 miles.  So far so good. See you in about 1000 miles.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by TheSneeze on 06/07/22 at 07:31:14 Having to wait 8 weeks for my cylinder head is killing me!  I am really anxious to get my engine back together.  The head is the last piece of the puzzle I need.  As always, great write up, DBM!

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by Armen on 06/07/22 at 07:35:55 Awesome write up! Thanks again!!!

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by ohiomoto on 06/07/22 at 16:33:53 I think people should pay attention to the color of your spark plug.  I'm thinking your plug is cleaner than 9 out of 10 plugs on here.   I haven't pulled mine in 3 or 4 years.  I'm running leaner jetting than most on here and I bet mine still shows more carbon than yours.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 06/08/22 at 11:03:07 On the LS, I have never been able to get my sparkplug to color correctly.  With unleaded fuel, the thing should be much lighter than it is.   Don't know why it's so dark.  I used to think it was due to not having any quench, but that's not the case anymore.  I've been using the wide-band O2 sensor for a long time now.  That, combined with diligent timed run checks, gives me good confidence that my air/fuel ratio is very close to optimum.   On this engine, the spark plug just runs darker than I would like.  It also has more deposits than I normally see with unleaded fuel.  I guess oil consumption might play a role, but coloration and deposits were the same when it wasn't consuming any oil. Must be a nuclear phenomenon.

Title: Re: Wiseco Flat Top Piston - Installation & Te Post by Dave on 06/09/22 at 03:37:57 Great write up and research as usual. Is is possible that modern fuels don't create the same color on the insulator that we are use to seeing? I can remember in the old days of leaded fuels seeing the inside of my exhaust pipe being a light gray color after a long trip where the system had been up to temperature for an extended period......now the tailpipe is always soot black.  Similarly the exhaust valves are ghost white - and I used to think a nice tan color was normal for the valves in a healthy engine.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 06/30/22 at 22:54:48 32,251 Miles Time for the next service.  The 94mm flat-top now had 7000 miles on it (actually 9250 miles if you consider the 2250 miles I logged on the first build).  It had been running perfectly.  Power was great, noise & vibration normal, temperatures normal (180 oil/280 CHT), oil pressure normal (7psi with 200°F oil temp @ 4000 rpm, down about 1 psi due to the KrankVent), fuel economy excellent, and oil consumption the same (about 8 ounces every 1100 miles).

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 06/30/22 at 22:55:39 I had just finished a long ride and reached the 7000 mile mark.  I decided that it might be a good idea to do a “HOT” compression check before I dumped the oil.  I generally do my compression checks cold and had never tried to do a hot check.  So, I pulled into my garage, set the bike up in the stand, pulled off the seat and fuel tank, quickly removed the spark plug, and did a compression check. Shazaaaam!  That sucker pumped 245 psi.  Either I’ve got a big pile of carbon built up, or that “HOT” check makes one helluvalot of difference.  On the last service, it was 225 psi cold.  Best check compression again (cold).

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 06/30/22 at 22:56:27 The oil dump went well.  No chunks of metal on the drain plug.  One interesting tidbit, it wouldn’t drain when I removed the plug.  Aha!  The KrankVent.  Had to remove the fill plug to vent the crankcase.  It drained like gangbusters once I removed the fill plug.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 06/30/22 at 22:56:58 A quick wipe with a paper towel showed that no significant flakes or chunks were on the drain plug.  The sludge simply smeared onto the towel.  There were no particles that had any visible dimension.  Just sludge/dust.  No indications of gear failure.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 06/30/22 at 22:57:58 I surveyed the drain pan with an ultra-strong magnet.  I wanted to see if any chunks came out with the oil.  I spent a long-time fishing around in that drain pan.  Every square centimeter was swept with the magnet.  Zero particles.  This engine seems to be holding up well.  Under reasonable riding conditions, the engine and transmission are handling the increased torque.  Granted, it’s not as much torque as the 97mm flat-top, but based on acceleration times, it’s very close.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 06/30/22 at 22:58:38 The spark plug looked the same as it did at 3500 miles.  It was darker than I would prefer, and the ground electrode was a super-light grey, some would say white.  It’s not the sort of coloration I am used to, but it seems normal for this engine.  No balls of metal.  No melted cement.  No fractures in the insulator.  No tell-tale signs of detonation.  All good.  The gap was .033”.  I left it as-is.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 06/30/22 at 22:59:19 When I popped off the clutch cover, I could see right away that the free-floating tensioner was stroking.  There was a polished ring around the plunger indicating that it was doing a lot of in & out movement.  The Tahitian Hula.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 06/30/22 at 23:00:05 To check the plunger extension with this tensioner system, you must load up the forward side of the cam chain in order to ensure that the rear side is slack.  That’s easy to do.  Just rotate the engine in the normal direction of rotation until the intake valves start to open.  That loads up the forward side of the chain (drive side) and ensures that the rear side of the chain (slack side) is loose.  Now the tensioner plunger is completely extended. So, position the intake valves about half-open.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 06/30/22 at 23:00:58 Then measure the plunger extension.  My tensioner was now extended 14mm and had 3.5mm back-travel.  IMO, that’s too much back-travel to maintain proper valve control.  Looks like this thing needs attention about every 7000 miles.  It’s easy to do so no big deal.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 06/30/22 at 23:02:08 I had to turn the jack bolt in 3-turns in order to restore the tensioner extension to 12mm.  That provides 1.5mm (.06”) back-travel on the plunger.  When the cylinder heats up and grows, it should tighten up the chain drive and the tensioner will have almost no back-travel.  As the system wears, the tensioner will extend and the back-travel will increase.  I plan to keep the back-travel below 4mm (.16”) by periodically adjusting the jack bolt. I still have to be concerned about chain guide wear.  As I continue to turn in the jack bolt, the arc of the rear guide will get tighter.  That will change the angle of entry between the cam sprocket and the chain, and I suspect subject the rear guide to accelerated wear.  These periodic checks will help me project how quickly the plunger extension will increase. This shows how much I had to turn in the jack bolt.  The distance between the red plastic on the pin gage and the end of the bolt is about 3mm (1/8”).

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 06/30/22 at 23:02:45 Once adjusted, the jack bolt is locked in place with the cap, which is sort of a fancy acorn nut.  A light coat of sealant keeps it oil-tight.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 06/30/22 at 23:03:25 Things could get ugly real fast if the jack bolt ever came loose, so safety wire is mandatory.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 06/30/22 at 23:03:53 The valve clearance remained unchanged.  The intakes were still .005” and the exhausts were still .006”.  This bodes well for the DR650 cam and the Cagiva valve adjusters.  Doesn’t look like anything is wearing down.   The heavy-duty RD springs don’t seem to be causing any issues.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 06/30/22 at 23:04:49 The 13-plate hybrid clutch looked fine.  I’m not going to disassemble the clutch unless it exhibits some sort of problem (slipping, dragging, noise, etc.).  Up to now, the clutch has performed well.  It never slips.  The drag is actually less than the stock clutch.  Shifting is good.  No problems finding neutral.  The only anomaly is an occasional squeal that occurs if I try to take off in the wrong gear or do a jack-rabbit start.  I think that is due to my leaving the wave-washer assembly out of the stack.  I think that results in a bit of chatter and/or resonance.  Not a problem IMO.  Dave is also experiencing this squeal on his 13-plate mod.  He might have additional comments. The hybrid clutch hacks the mission.  I continue to beat this thing up pretty good, and it doesn’t slip.  Takes a lickin and keeps on tickin.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 06/30/22 at 23:05:35 The special Sneezy clutch release cam continues to work like a charm.  The ball socket looks the same as it did when I installed it.  The action has been smooth and consistent.  It never needs adjustment.  It’s stronger than dirt.  What more can you ask for?  If you don’t have a Sneezy cam, you do so at your own peril.  Thank you again Mr. Sneezy.  Killer good replacement part.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 06/30/22 at 23:06:17 The clutch pushrod is also in excellent condition.  It performs well with the Sneezy cam.  One part is not sacrificial to the other.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 06/30/22 at 23:06:59 The epoxy in the intake port looks exactly as it did 7000 miles ago.  The small crack hasn’t changed.  I can’t forget about the epoxy; that would be foolish.  But it has held up admirably for about 15,500 miles.  I will continue to inspect it periodically.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 06/30/22 at 23:07:39 Awhile back my intake elbow fell apart.  It was a 2” street elbow made from ABS plastic.  Best as I could figure, the aromatics in the fuel attacked the plastic and it crumbled apart.  I replaced it with a 2” PVC street elbow.  I didn’t like the look of the white PVC, so I painted the replacement elbow with black paint.  The PVC elbow is holding up well.  It has yellowed on the interior, but there is no evidence of deterioration.  It’s also clean as a whistle.  Zero dirt.  The K&N filter is takin care of business.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 06/30/22 at 23:08:22 Like the induction elbow, the carburetor was very clean.  No dust or dirt accumulation.  The PWK carburetor is proving to be very reliable and consistent.  It never requires adjustment and continues to provide great performance from idle all the way through WOT.  No hiccups, smooth response, no flat spots or hesitation, killer power & economy.  I never touch the thing.  What a bargain.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 06/30/22 at 23:09:21 The special earth-friendly breather system is working well.  There doesn’t seem to be any improvement in performance, but it definitely dried up all the little oil weeps and seeps.  The joints are 100% oil-tight.   The catch can drain down was interesting.  A small spurt of brown liquid dribbled out.  This liquid was way too thin to be engine oil.  The liquid seemed to be about the viscosity of penetrating oil.  Only thing I can figure is the aromatics off the carburetor circulate into the breather system when the engine is secured.  There they mix with any oil droplets in the catch can screen and drip into the reservoir below.  It’s a very small amount of liquid.  Since my catch can is fabricated from ABS plastic, I need to be concerned about a failure similar to the one I experienced with the ABS induction elbow.  While it wouldn’t threaten the engine, it could be messy.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 06/30/22 at 23:10:36 Fuel economy did not improve.  I thought I could get a few more mpg with a tad more ignition advance.  That didn’t pan out.  The additional 2° of ignition advance didn’t do much.  Temps may have come down a bit, but fuel economy didn’t improve.  Neither did power.  Same goes for the new muffler.  The 1.75” baffle flows a lot better than the 1.65” baffle, but I didn’t realize any appreciable gains in performance or economy. Over 3589 miles I filled the tank 30 times.  It used 53.0 gallons of premium fuel.  That works out to an average 67.7 mpg.  The worst mileage I got over that period was 61.4 mpg.  The best I got was 73.1 mpg.   It still gets really good fuel economy; I just can’t replicate the economy I was getting with the 340b cam, VM carb, and light flywheel.   Oh well. After it was back together, I filled it with Mobile 1 and did a cold compression check.  It pumped 225 psi.  That pretty much confirms that hot checks pump way more than cold checks.  Looks like I can expect about 9% more cranking pressure when it’s hot.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 06/30/22 at 23:11:20 So far so good.  All is well with the Hotrod Savage.  I’m currently at 32,641 miles.  Next oil change will be due at 35,751 miles.  It’s running great.  See you in about 3100 miles.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by TheSneeze on 07/01/22 at 07:42:16 Thanks for the practical testing and kind words, DBM.  After running a metal fab shop for 24 years, I knew the material selection was the right way to go and it would be waaaay stronger than the sintered stock part.  There was a lot of jibber jabber initially about test methods and whatnot.  But I appreciate you doing the test work and publishing the results - it verified what I knew to be a much stronger part.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by justin_o_guy2 on 07/01/22 at 08:31:04 7C7A75090B0C08380 wrote: Awhile back my intake elbow fell apart.  It was a 2” street elbow made from ABS plastic.  Best as I could figure, the aromatics in the fuel attacked the plastic and it crumbled apart.  I replaced it with a 2” PVC street elbow.  I didn’t like the look of the white PVC, so I painted the replacement elbow with black paint.  The PVC elbow is holding up well.  It has yellowed on the interior, but there is no evidence of deterioration.  It’s also clean as a whistle.  Zero dirt.  The K&N filter is takin care of business. If you ever need to replace it, have a look at CPVC. That is what you use for hot water. I don't know if JB weld is like bondo, except that it is an epoxy. If you're looking at a place that just won't straighten enough to only need a shallow application of bondo and you Have to apply a deep stack of bondo, you can't do it in one pass. It's gonna crack. You hafta put it on in layers. Naturally, clean and dry surface, then, pressing the bondo onto the surface, " Wetting "it, add enough to be able to scratch it with something like 40 grit,to give it Teeth so the next application will stick, rinse and repeat. If you could find something that would take the heat, be non metallic and flexible to use like rebar,that would be good. When I was working on a cab over truck that had been sand blasted using heavy media, I used six gallons of mud. Passenger side had been punched just above the headlight. The floor was buckled up. It was aluminum, I had nobody to hold a backup hammer while I smacked it from the other side. I don't remember how I got ahold of it to pull it with the come along, but I got it hooked up. It just slid the fork lift, so I grabbed a few welding rods,got the flux off of them and started building that area up until it was pretty deep, drilled a coupla holes and put a rod in the mix. Built it up more, added another rod, I think I used three, not sure anymore.. But the moral of the story is, my body man buddy told me I was going to see it crack and fall out. I saw that truck, up close, about five years later, when they retired it. No cracks. And it was a West Texas oilfield truck, so it got rattled hard goin down those roads. Ahh! And another thing about epoxies. Yeah, the instructions tell you how to mix it. But if I want it to not be brittle I use less hardener. Trying to get a large area covered in one pass is difficult, especially if it is a hot day. YaKnow, you can almost stop epoxy from curing by putting it in the freezer. If you want to try an experiment you could mix a batch and make three lumps. Smear half of one thin,leave some scooped together to make it thick In the freezer it goes Another of them, all from the same mixture Just leave it where you are working The third, in the sun and hopefully some breeze. I got a blister from some five minute epoxy I mixed up and had a fan blowing on it. If you mix it up light on the hardener you can put a drop light near it. My boss was pretty upset when I mixed up enough to cover the whole roof of a big four door car and it looked like it would never dry. Parked it in the sun, and about an hour later I had a roof with a uniform application of mud. Quick and easy to finish because it wasn't a patchwork of areas of varying hardness. never dry,,everyone does that once in a while..

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 07/05/22 at 11:19:32 Justin, thanks for the comments regarding mix ratios.  I use a JB Weld product called "High Heat" for the port mods.  It comes in a log with the two components already rolled up together.  When you want to use it, you kneed the log to mix the two components and then have about 8 minutes to apply the mixed epoxy.  It works good for this application because the mixture is firm and holds it's shape as you form it over the floor of the port.  To keep it from sticking to my finger, I wet my finger with mineral spirits. It doesn't surprise me that a crack developed.  I anticipated that the epoxy would eventually degrade.  It's subjected to a harsh environment.  The fuel acts as a solvent and is constantly bathing the surface of the epoxy.  There are extreme temperature swings from ambient when I start it to possibly about 300 degrees when it's at max temp.  There are also huge temperature gradients between the entrance of the port to the area adjacent to the valve seats, and also from the surface of the epoxy that's getting bathed in vaporizing fuel to the bond joint between the aluminum and epoxy.  To make things worse, the aluminum and epoxy expand at different rates.  I'm amazed that it has lasted as long as it has. The crack extends from the 8mm stud hole straight back to the entrance of the port.  The layer of epoxy in that area is real thin.  I'm not too worried about it.  It's easy to inspect so I'm just gonna keep an eye on it for now.  It would be nice if I had a little more working time with the epoxy so that I could shape it a bit better during the application.  Maybe I should play around with it a bit to see if I can figure out which component of the log is the hardener, then see if I can somehow scrape out a bit of the hardener and see it cures OK. This post has some info on the various epoxies/fillers I was considering and how I tested them prior to doing the port mods.  I believe that at the time I was trying to find a filler that was suitable for the exhaust port too.  As it turns out, I determined that the exhaust could be improved to a point that exceeds my requirements and no filler is needed in that dipsy-doodle.   http://suzukisavage.com/cgi-bin/YaBB.pl?num=1557210973

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 08/20/22 at 18:08:14 35,783 Miles.  Time for the next service.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 08/20/22 at 18:09:06 Although my focus was on the engine, the test program was taking a toll on the rest of the bike.  I was logging a lot of miles, trying to click off at least 120 miles per ride, and trying to ride at least five times per week.  A few other things were gonna need some attention. Tires for one.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 08/20/22 at 18:09:41 The front was worse.  I really shouldn’t have been riding on these old tires.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 08/20/22 at 18:10:23 The front brake rotor had reached the wear limit (4mm or .16”).  I was gonna be busy.  Man, that’s one ugly fork leg.  Cosmetic issue, not a concern.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 08/20/22 at 18:12:08 Regarding the engine, the 94mm flat-top now had 10,000 miles on it (actually 12,250 miles if you consider the 2250 miles I logged on the first build).  It was running well.  Power was great, vibration normal, temperatures normal (180 oil/280 CHT), oil pressure normal (7psi @ 4000 rpm with 200°F oil temp), fuel economy excellent, and oil consumption the same (about 8 ounces every 1100 miles).   But noise levels were up significantly, and the clutch was getting real grabby and unpredictable. At around 8500 miles, it started rattling.  I thought it might be developing some piston slap.  After all, the cylinder had been honed several times for various projects, and I lean toward the loose side on forged pistons.  But by the 10,000-mile mark that sucker was making a loud metallic rattle.  The rattle was most pronounced when I throttled up in neutral.  This was more than just some minor piston slap.  I needed to address the noise immediately.  This YouTube vid tells the story. https://www.youtube.com/shorts/KUhN_OHQhmo The clutch noise (squeal) I reported at the 7000-mile inspection was now louder.  And as I mentioned, the clutch was starting to get grabby and unpredictable.  I could live with it, but the average bear wouldn’t like the lack of a smooth progressive engagement.  Time to take a look.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 08/20/22 at 18:14:13 First order of business was a compression check.  I was so focused on the loud metallic rattle that I wasn’t thinking straight.  I had just pulled into the garage from a long ride.  The engine was hot.  I pulled off the seat and the fuel tank, removed the spark plug, installed the compression gage, and did the test.  The thumper pumped a dismal 105 psi. :o Seriously, 105 psi?  Try again, 105 psi.  Again, 105 psi.  Huh?  Again, 105 psi. I was anxious and getting all worked up.  Calm down Mike.  There must be a good explanation for this dismal squeeze.  Put on your big boy pants and get your head straightened out.  Eureka!  You know better than to do a compression check with the throttle closed.   Open the throttle all the way when you check compression, it makes a BIG difference. OK.  It pumped 215 psi.  Still a concern.  I lost 30 pounds of squeeze since the 7000-mile service. No need to panic.  It’s runnin superb, so I figure this is an anomaly.  We shall see how things shake out.  Focus on the noise.  The two may be related.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 08/20/22 at 18:14:57 The spark plug looked the same.  Nothing to be concerned over, but I would prefer a cleaner plug.  I run unleaded fuel.  These deposits don’t seem normal to me, but my Savage has always had a dirty lookin plug, even when it was stock and super-lean.  Gap was about .034” to .035”.  I reset the gap to .031”.  This is a very old spark plug, but it works just fine so it’s goin back in.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 08/20/22 at 18:15:26 I dumped the oil while it was still good & hot.  Ouch!  I hate dumpin red hot oil.  The drain plug looked great.  No chunks, just magnetic sludge.  I guess the 5-speed can handle the flat-top piston’s power as long as you ride the thing like a normal biker.  I love my daily dose of acceleration, and nothin beats a little WOT 5th gear pass, but I’ve been more restrained than I was with the other bottom end.  It’s getting a good workout, just not continuously.  Things look solid.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 08/20/22 at 18:15:55 Valve clearance was still .005” intakes and .006” exhausts.  The Cagiva valve adjusters are working really good, and the valve train does not appear to be wearing.  Based on the study I recently did on the effect of valve lash on valve closing velocity, I reset all the valves to .003”.  Let’s take it easy on those valves, place them on the seat gently, respect those heavy RD springs.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 08/20/22 at 18:16:45 Time to pop off the clutch cover and check the cam chain adjuster, clutch, and primary drive.  What could be causing that loud metallic rattle. The cam chain adjuster was at 13.5mm extension.  Same polished area on the plunger.  This thing will need attention every service.  It’s not the source of my noise, and it’s not extended enough to cause concern over valve control, but by the next 3500-mile service it will be.  Easy enough to adjust.  I turned my jack-bolt in 1.5 turns to bring the extension right back to 12mm.  I’m not a fan of this thing stroking in & out as the engine rotates, but it’s not causing any problems, and the jack-bolt makes it super-easy to adjust.  I’ll keep it.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 08/20/22 at 18:17:22 I didn’t find anything of concern in the clutch.  One of the seven fiber plates had a little bit of grooving in the friction material.  The other six plates looked brand new.  They were all .115” thick, right up to factory fresh spec.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 08/20/22 at 18:17:57 The steel plates all looked great.

Title: Re: Wiseco Flat Top Piston - Installation & Te Post by DragBikeMike on 08/20/22 at 18:18:32 The clutch basket looked good to me.  It wasn’t loose on the input shaft spacer.  The bronze bushing had no visual indication of distress or wear.  It wasn’t pinched between the input shaft thrust washers, and the thrust faces were smooth.  No unusual wear or notching on the tangs.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 08/20/22 at 18:19:07 The cushion springs in the clutch basket drive looked fine.  None broken or missing.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 08/20/22 at 18:19:45 The clutch hub flange was smooth, and the nut was good and tight.  Nothing here to explain the grabby engagement or the squealing noise.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 08/20/22 at 18:20:26 Same for the pressure disk.  Flange smooth, nothing unusual.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 08/20/22 at 18:21:03 The input shaft spacer and thrust washers had a little fretting or scoring.  The hub nut was tight when I disassembled the clutch, and the basket turned smooth as silk on the input shaft spacer.  Could the sleeve and/or washers be turning with the basket?  I guess it’s conceivable that I might need a little more thrust clearance, but it would be tricky to add a few more thousandths of an inch.   I guess I could try a stepped washer, or possibly manufacture a slightly longer spacer.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 08/20/22 at 18:21:39 The only thing I found of any significance was the o-ring on the push piece.  I could tell as soon as I went to pull the release plate and push piece that it was loose.  The push piece came out of the input shaft with zero resistance.  It essentially fell out.  My experience with this o-ring has been that it fits super-tight into the input shaft.  Visual inspection revealed a flat o-ring.  It was worn out.  A leak here might reduce oil pressure at the input shaft spacer, clutch basket bushings, and thrust washer.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 08/20/22 at 18:22:19 I replaced the o-ring and reassembled the clutch.  I didn’t even clean it.  It went back together with the same dirt it had when I took it apart.  Other than the o-ring, I couldn’t find anything conclusive.  Whatever is going on will be revealed when it breaks.  But for now, it all looked good to go.  The clutch holds the power just fine.  It doesn’t slip at all.  But the grabby engagement and squealing noise are a bit unnerving.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 08/20/22 at 18:23:00 What’s causing the rattling noise?  While I was under the clutch cover, I checked torque on the primary drive nut and the balance shaft bolt.  They were right up to spec.  The only easy thing left to check was the flywheel.  I pulled off the alternator cover, alternator rotor, and the starter drive.  The flywheel looked tight, and I couldn’t rotate the nut with my fingers.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 08/20/22 at 18:24:00 But this flywheel weighs six pounds.  Best check the nut with a proper wrench.  That darned nut was dead loose.  I bet it didn’t even have 10 ft-lbs on it.  I pulled the flywheel off to inspect the splines.  The face of the flywheel shoulder had a little scoring but nothing to be concerned about.  It was clearly moving on the splines.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 08/20/22 at 18:24:39 The splines looked good.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 08/20/22 at 18:25:37 I’m not going to go into a lot of gory details, but IMO the heavy flywheel doesn’t work well with this high compression engine.  I’ve raised the squeeze from 8.5:1 to 10.5:1.  That results in a big change in the acceleration/deceleration rates during the power stroke and the compression stroke.  It works the nut loose. While I had the flywheel off, I checked the up & down movement of the crankshaft.  It was .002” when I installed this engine.  After 10,000 miles it was still .002”.  I don’t think my rattling noise was the main bearing.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 08/20/22 at 18:26:41 If you recall, I switched to the stock flywheel just to be safe.  I had some weird stuff goin on with the bearing bores in my other engine.  There was a remote possibility that the mini flywheel might have had something to do with mysterious bearing bore anomalies. After lots of research and thorough inspection, I haven’t been able to establish any correlation between my messed-up bearing bores in the other engine and the 3-inch flywheel.   I decided to install the 3-incher on this engine and see how things shake out.  So, on went the mini wheel.  It got torqued to 110 ft-lbs.  You need the correct tools to do this job.  No more rattle wrenches for me.  When I start this thing up, I will know immediately if the mysterious rattle was the loose flywheel.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 08/20/22 at 18:27:22 Time to take a quick look at the breather catch-can.  I haven’t touched this thing since the 7000-mile service.  Almost nothing came out when I pulled the drain plug.  This system works good.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 08/20/22 at 18:30:03 Time to put it back together and see if I corrected the loud metallic rattle.  Since I had the fuel tank off, I decided to lubricate my speedo cable.  I used a very light coat of moly lube.  Anyone have any thoughts on that? It fired right up.  I immediately knew that the flywheel repair was successful.  The loud metallic rattle was gone.  The engine now sounds normal, quiet for a Savage. The clutch squeal is gone, and engagement is smooth and progressive.  What the heck fixed that?  I’ve put about 300 miles on it since completing the service.  It’s still working perfect.  Might have been the push piece o-ring.  If it acts up again, I will focus on the input shaft spacer, thrust washers, and push piece o-ring.  It has a generic nitrile o-ring in it now.  I need to order a few of the genuine Suzuki o-rings. I got so worked up over the noise and the clutch that I never inspected the intake port epoxy.  I’ll check that next time. The PWK carb is still working great.  I did finally have to adjust it.  The light flywheel brought the idle down to about 1000 rpm.  I like it about 1300 to 1400, so I had to raise it up a bit.  First time I’ve touched the carb in a very long time. The old S40 got a new set of rubber and a new front brake rotor.  Ready for safety check.  Amazing how much better it handles with new tires.  I installed Dunlop 404s.  Those were a $itch to mount.  Way harder than the stock IRCs.  It’s difficult to get tires out here.  Shipping is through the roof.  I don’t like the aspect ratio on the rear Dunlop, it’s too tall.  But I must admit, it handles nice with these new tires.  Cruising rpm is a little more relaxed too, but acceleration is a bit slower.  What ya gonna do?  Play the hand your dealt. My plan was to tear the engine down at the 10,000-mile mark, but the Big Bore 4-speed isn’t ready yet, and this 94mm Flat-Top is runnin sweet.  I’m gonna keep runnin it for a while.  I have to admit, with this one runnin so good I’ve lost motivation to work on the other one.  I must focus, get the big one finished. See you at 39,283 miles.  8-)

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by robb+ on 08/22/22 at 08:58:25 Thanks for posting this DBM. I'm going to follow your lead with using a lighter flywheel with the high-comp piston because your results are encouraging! Hoping for similar results with my noise. I'm learning that something else always starts acting up with incremental hot-rodding...

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by Armen on 08/22/22 at 09:26:56 Thanks for the detailed reporting! So, a million years ago I built a hotrod Bultaco that ran in 250 and 350 GP in AHRMA. The guy who owned the bike (my dear friend David) had some quirks. One of which was the insistence on running the stock, external rotor magneto. Insane. As the revs and HP went up, this rotating boat anchor was more and more of a liability. So, one year at Daytona, David gets towed back in with a dead motor. I pull off the left cover, and the magneto and the end of the crank fall out. The quick transitions from full on to full off were too much for the crank. As it was, Kevin Cameron (tech writer extraordinaire) was walking by and looked over. Before I could even ask what he thought, he said “What do you think?!?!”. So, I built a new crank, and we went to an internal rotor magneto. Problem solved. So, yeah, I like light flywheels  when you tweak the bikes.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by justin_o_guy2 on 08/22/22 at 13:57:38 As a copier tech I had to take things apart, disassembling it to get to where I thought the problem was. Get in there, studying everything for something wrong. After getting deep enough in to think maybe I was wrong, so, clean, lube,reassemble, test, Boom! Working, making great copies. The other techs experienced the same thing. I can accept that, it's a whole lot better than putting it together and Now it's Worse And you have no idea what you screwed up.

Title: Re: Wiseco Flat Top Piston - Installation & Te Post by DragBikeMike on 08/22/22 at 17:15:04 I hear what you are sayin Justin.  Don't look a gift horse in the mouth.  Time will tell. Armen, that old Taco sounds like it was killer.  You've mentioned it a time or two.  I'd really love to see it.  There was a simplicity in those old Spanish hotrods that made them extra special.  There were only a few out here in the late sixties and early seventies.  Can you post some pics in the Cafe, or maybe email a few to me? I always had a lot of respect for KC.  His articles in the old motorcycling publications were the best.  Always chock full of the theory behind the designs, loads of intricate and useful nuts & bolts meat & potatoes.  Cool that you got to hang with a guy like that. I just don't get this flywheel on the LS.  I've converted several dirt bikes to internal rotor mags.  The rev factor was always a major change.  The little ringdings would rev instantly when you snapped the throttle.  My Harley Evolution dragster was a totally different animal when I removed the charging system and went to total loss.  Like night & day, whack the twist grip, instant revs.  This LS..... take six pounds off the wheel and you can't even tell the difference.  Crazy. Regarding snapping off the crank, again I am totally bamboozled.  Look at the drive side vs the alternator side.  The alternator side is twice as robust, way more beef.  The left side also has that big, beefy roller bearing vs the whimpy ball bearing on the drive side.  But the drive side transmits all the torque, and also has to turn the cam.  Bizarre to say the least. If the alternator rotor and flywheel require that much shaft, there must be an inordinate amount of inertia to overcome, yet I can lob six pounds of dead weight off and nothing seems to change. You still chummy with KC.  Can you ask him?

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by Dave on 08/24/22 at 03:45:39 That darn flywheel nut can make a lot of noise when it comes loose.  I bought my bike used with 262 miles on it, and at 400 miles it started making a ticking noise - by 1,200 miles it was really banging. The source of the noise was impossible to trace by listening.  The flywheel noise transfers through the crank to the bearings - and then to the entire engine case.  For me the noise was worse at idle and at steady cruising speeds it was less noticeable.  I pulled the engine and started at the top and worked my way down inspecting parts as they came off - as you can guess I had the engine pretty well torn down before I discovered the loose flywheel nut.  When the bike went back together it got the engine improvements (95mm Wiseco, ported head,Stage 1 cam) - that was 15,000 miles ago. I am currently running the ultra light flywheel - but I likely had 10,000 miles with the stock flywheel when I put the light one on.  When I installed the stock flywheel I used the permanent red thread locker to help keep the nut tight.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/20/22 at 18:02:54 39,357 miles.  Time for the next service.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/20/22 at 18:04:00 The 94mm flat-top now had over 14,000 miles on it (actually 16,250 miles if you consider the 2250 miles I logged on the first build).  It was running exceedingly well.  Power was great, vibration normal, temperatures normal (180 oil/280 CHT), oil pressure normal (7psi @ 4000 rpm with 200°F oil temp), fuel economy excellent, and oil consumption the same (about 8 ounces every 1100 miles).   No more problems with flywheel noise.  The engine mechanical noise was normal (I would say on the quiet side for a Savage). The grabby clutch was a thing of the past.  The clutch was performing perfectly.  Smooth, predictable engagement, no more grabby nonsense, no more squealing noise. The new rear tire robbed a bit of my acceleration.  It has a larger rolling diameter due to the larger aspect ratio.  It brought my cruising rpm down a bit, and you could tell it had a little bit less giddy-up-go.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/20/22 at 18:04:43 At about 36,800 miles I installed a 25T pulley to see how the thing would run with even taller gearing.  Dave’s kit had everything I needed to do the install.  The pulley looked great, all nicely powder coated.  It fit like a glove, not a millimeter to spare.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/20/22 at 18:05:57 The 25T pulley worked fine.  No rubs, no whine.  It took its toll on my acceleration.  Really slows the little rocket down.  It also has a big impact on your odometer readings.  Now, when you ride 114 miles the odo will only read 100.  Be careful, don’t run outa gas. I have mixed feelings about the 25T pulley combined with that big 190 rear tire.  It feels way less powerful.  I miss the instant acceleration…..but…..I’m loving the 4 or 5 hundred rpm drop when cruising the freeway.  Given my current mode of operation, I’m thinkin I will become fond of the big pulley.  I’m surprised that I didn’t see any sort of improved fuel economy.  I have to correct my odo readings by a factor of 1.138, but even with the CF I still don’t see any fuel mileage improvement. It will be interesting to see what happens when I run the big pulley with the 4-speed.  Top gear on the 4-speed is just a smidge taller than top gear on the 5-speed, plus the 4-speed is wide ratio.  Might be a dog with that big pulley and big tire. When I swapped out the pulleys, I was able to inspect the splines for fretting corrosion.  Sweet!   No red powder.  All looks good.  The moly lube is a decent fix.  Just under 12,000 miles and they look the same as the day I slathered em up with the black gold.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/20/22 at 18:07:14 The remainder of the 3500 miles was uneventful.  That 94mm flat-top ran perfectly.  The Big Bore 4-speed was ready to go so this was the last inspection for the 94mm flat-top.  Let’s see how things looked. First order of biz was a compression check.   As you recall, it only pumped 215 psi last time.  That was with the engine hot.  After an additional 3500 miles on the odo (about 4000 when corrected for the taller gearing), that sucker had degraded to 205 psi (cold).  I guess maybe it’s holdin steady (hot should be higher than cold).  It’s certainly lower than I started with.  Unfortunate indeed, but what the heck, it runs great.   I have to admit, I wasn’t likin what I was seein.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/20/22 at 18:07:44 The spark plug looked the same as it has every time I pulled it.  Dirty & on the dark side.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/20/22 at 18:08:21 I dumped the oil and inspected the magnetic drain plug.  No evidence of impending doom.  Just magnetic fuzz.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/20/22 at 18:09:04 Wiped it on a paper towel.  No chunks, just mud.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/20/22 at 18:09:40 Dumped the catch can.  Maybe one-quarter of a teaspoon came out.  Just a teeny-weeny bit.  All good here.  I love this breather system.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/20/22 at 18:10:04 Valve clearance was still .003” all the way around.  The Cagiva valve adjusters seemed to be working well, and the valve train does not appear to be wearing.   We shall see when the head cover comes off.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/20/22 at 18:10:47 Time to pull the clutch cover and see what’s cookin in there. The cam chain tensioner was right at 12.5mm.  The trend is very consistent.  It’s extending right around 1.0 to 1.5 mm every 3500 miles on the odo.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/20/22 at 18:11:27 The clutch push piece o-ring was OK but did seem to be goin a bit flat.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/20/22 at 18:12:06 I verified that the clutch hub nut was tight before I removed it.  It was plenty tight.  All the clutch plates were perfect.  No change there. The clutch sleeve and thrust washers have quite a bit of fretting/scoring.  I’m gonna change those.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/20/22 at 18:12:35 Sneezy’s release cam is still perfect.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/20/22 at 18:13:09 On the other side, the flywheel nut didn’t move a bit when I applied 110 ft-lbs.  That mini-wheel just doesn’t store enough inertia to work the nut loose.  I don’t think I will have any more problems with the flywheel nut.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/20/22 at 18:14:05 Time to look under the head cover. The old DR cam still looked great.  The micro-pits are just getting to the point where you can see them with the naked eye.  The cam currently has a little over 26,000 miles on it, and many of those miles were logged with the heavy RD springs.  I’m gonna continue to run this cam and see how long it lasts. You can just see the pitting in the intake lobe.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/20/22 at 18:14:38 The exhaust lobe is just a bit better than the intake.  Still serviceable but of course I would prefer zero pits.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/20/22 at 18:15:16 The rocker pads are pristine.  They look like they are right out of the box.  I love these late model rocker arms.  They can take the abuse.  No problems here.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/20/22 at 18:16:14 The Cagiva valve adjusters are a flop.  They pitted out.  I suspect that’s due to the tighter radius.  It increases the pressure at the point of contact.  I guess I have to revert back to the stock adjusters.  I don’t have any plans for running the heavy springs.  You need the heavy springs for the bigger cams (Web 340b & 402), but I’m done with those.  They just don’t hold up.  The OEM DR650 cam (with lower lift) is designed to run with the same springs and same valve adjusters as the LS, so I’m thinkin the stock adjusters should serve me well moving forward. Here's a look at the intake adjusters.  The left-hand adjuster has an ugly pit.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/20/22 at 18:16:53 Same problem on the exhaust end, only the pit is in the right-hand adjuster. That’s a nasty pit.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/20/22 at 18:17:39 As expected, the valve tips didn’t fare any better.   The left-hand intake has a fairly deep pocket worn into the tip.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/20/22 at 18:18:13 And the right-hand exhaust tip is a bit worse.  This will be a good opportunity to see if I can fabricate a rig to grind the valve tips.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/20/22 at 18:18:50 The cam chain measured out at 5.01” over 21 pins, well below the wear limit of 5.07”.  The jack bolt adjuster is working great.  It’s part of my scheduled maintenance routine.  Change oil, adjust valves, and inspect the cam chain tensioner every 3500 miles.  Adjust as necessary.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/20/22 at 18:19:24 When I measure chain wear, this setup helps a lot.  Use two cam sprockets and a ten-pound weight to consistently take all the play out of the chain.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/20/22 at 18:20:03 The chain guides look good too.  I suspect there is at least 30,000 miles on these.  No cracks.  No wear.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/20/22 at 18:20:49 The cylinder head looked pretty good.  No evidence of a valve problem that would explain why the squeeze was down a bit.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/20/22 at 18:21:27 Time to do a quick & dirty check.  Set the head up on a flat surface and use a small bubble level to level the head.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/20/22 at 18:22:02 Fill the combustion chamber with solvent with a little oil mixed in (about 10:1).

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/20/22 at 18:22:38 Start timing.  You want to leave it sit for at least five minutes.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/20/22 at 18:23:17 Watch the level of solvent in the combustion chamber.  If the level drops in five minutes you have a problem.   Periodically look into the ports for signs of solvent under the valves.  If it’s leaking, you will be able to see it.  Hold the test for at least five minutes.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/20/22 at 18:23:55 The level of solvent in the combustion chamber didn’t drop a bit, and there was no evidence of wetting inside the ports.  My drop in compression is not a result of leaky valves.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/20/22 at 18:25:50 The 8mm head stud just below the exhaust port is sitting proud.  A tool bit snags on the edge of the stud.  The internal threads in the aluminum head are giving up.  I discuss this in another post on head fasteners and how to repair them. http://suzukisavage.com/cgi-bin/YaBB.pl?num=1665791582 See how the tool bit snags on the edge of the stud.  The stud is proud about .007”.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/20/22 at 18:26:32 There’s a corresponding impression on the top of the cylinder.  The stud must be repaired to maintain a tight joint between the head and cylinder.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/20/22 at 18:27:10 The top of the piston was pristine.  Almost no carbon accumulation after more than 14,000 miles.  The flat-top piston really runs clean.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/20/22 at 18:27:50 Time to get a good look at the guts.  IMO, the best way to remove the cylinder is with wooden wedges.  You don’t wanna be bangin on the cooling fins.  The wedges apply even pressure.  Just gently tap the wedges together and as the stack gets taller the cylinder breaks loose from the case.  Easy.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/20/22 at 18:28:24 My cylinder had telltale marks in the bore.  Although you can’t catch your fingernail on any of the marks, and a very light honing will most likely clean them up, I’m not likin the look of this.  It’s lookin like an issue with debris from the crank case.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/20/22 at 18:29:05 The wrist pin was a bit difficult to remove, typical of an in-service piston with a full-floating wrist pin.  All you need is a PVC coupling and a jack bolt assembly.  Go slow, don’t wanna damage the piston or the rod.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/20/22 at 18:29:42 The piston looks great.  Not a blemish anywhere.  You can still see and feel the tool marks from the manufacturing process.  Piston rings look good too, but I suspect they are the cause of my lower than anticipated compression pressure.  Wrist pin is in good shape.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/20/22 at 18:30:13 The piston measured out right at 3.6985”, exactly what the detailed drawing specifies.  Couldn’t ask for any better after 16,000 miles.  No coking on the underside, it runs cool.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/20/22 at 18:30:47 The pin bores looked good, a few superficial marks from pin removal.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/20/22 at 18:31:28 The left-hand crank runout was almost .003” TIR (about .0028”).  That’s up a bit.  As I recall it was on the order of .0020” TIR when I installed this engine.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/20/22 at 18:32:00 Left-hand bearing play was about .0025” up & down.  That’s a bit more than it was.  When I installed the engine, it was .0020”.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/20/22 at 18:32:30 On the right-hand side, the crank runout was pretty much zero.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/20/22 at 18:33:05 The right-hand main bearing play was .0005”.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/20/22 at 18:33:37 The wrist pin bore in the crank looked great.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/20/22 at 18:34:54 This whole project was essentially a recovery from my Big Bore Flat-Top engine 5th gear failure.  On the Big Bore engine, 5th gear pitted badly, and chunks of the gear teeth ended up in my cylinder.  Those steel particles chewed up the cylinder and the marks in the cylinder, although much deeper and far from superficial, looked similar to the marks I am seeing in this engine’s cylinder.  A gear inspection was in order. I took a long, hard look at 5th gear on the input shaft.  It looked perfect.  But because of the failure on the Big Bore, I have been restricting the WOT operation on this 94mm Flat-Top engine.  These days, I reserve the WOT stuff for 1st through 4th.  So, it seemed prudent to also take a long, hard look at 4th gear. Oh my!  Lucky I took a look.  My 4th gear was pitted severely.  Smaller engine, a little less steam, but the gears still can’t handle the torque.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/20/22 at 18:35:29 How am I gonna fix this issue?

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/20/22 at 18:36:53 IMO, this pitting is the result of overloading.  There might not be sufficient lubrication to handle the increased torque, or the material that the gears are made from might not be up to the job, or the tooth profile might not provide sufficient load bearing surface area to distribute the load.  It could be a combination of all three. The transmission gears rely solely on oil thrown off the connecting rod bearing.  The gears don’t dip into the sump, and the pressure feed into the hollow shafts only provides oil to the bores of the gears.  None of that pressure fed oil is getting into the gear mesh. The gears on the input shaft block the gears on the output shaft from the oil being thrown off the rod bearing.  The larger input gears (4th & 5th) operate at a much higher velocity due to their larger circumference.  At high speed, the velocity of the gear teeth is very high, and any oil that gets thrown onto the teeth must overcome high centrifugal force in order to stay on the teeth and run through the mesh.  At high speed the load is also highest, so the tooth pressure is at max.  The perfect storm. The old 4-speed has gears that are more robust.  The teeth are wider and thicker.  If I’m lucky, the material they used in the old days was better (like maybe 4340 instead or 4130 or something like that). I would be forever grateful if any of you with engines on the deck could take a peek into the trans.  You can see all the input gears through the opening in the case.  Do any of you have pits in your gears?  Are there pits like the ones shown in my pictures?  If you have pits, please post some photos, and maybe provide whatever history you have on the engine (4-speed, 5-speed, oil used, mileage, how it was operated, mods, etc.).

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/20/22 at 18:37:32 The knock-off PWK has performed flawlessly throughout this project.  It never needs adjustment.  Starts fast, idles smooth, excellent cruising, perfect WOT performance, and superb fuel economy.  No surging, minimal afterfire (cackle crackle). It’s pretty dirty on the outside.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/20/22 at 18:38:01 But the inside is pristine.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/20/22 at 18:38:33 The slide has some wear-thru on the edges of the chrome plating but it still operates smooth.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/20/22 at 18:39:02 The slide needle looks great, no discernable wear.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/20/22 at 18:39:33 The slide channel in the carb body has a tiny bit of scoring typical of a slide type carb.  As I mentioned, the operation is smooth.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/20/22 at 18:40:09 The LCGP muffler is lookin a bit funky but I assure you it will polish up nicely.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/20/22 at 18:40:47 And the Mac header is a bit stained from rides in the rain on muddy roads.  It will clean up beautifully with a little Skotchbrite and a coat of VHT.  I love this Mac header with the black flame sprayed coating

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/20/22 at 18:41:22 The duplex rear pulley bearing is as smooth as the day I installed it, and it still looks good to.  Score one for the Chinese.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/20/22 at 18:42:03 The Big Bore 4-speed is in my bike now and it has about 300 miles on it.  It’s a special contraption with a pop-top piston, not a flat-top.  It will probably make a bit less steam than the 97mm flat-top, but about the same amount of steam as the 94mm flat-top.  While I test that engine, I’m gonna try to figure out a fix for this transmission issue. I hope this post is beneficial to some of you.  This was a great project and I really enjoyed spending hours & hours in the saddle.  I’ve learned a lot.  I intend to come up with a fix for the trans because I much prefer the 5-speed to the 4-speed (based on the limited time I have spent on the 4-speed).  I’ve already got a few ideas and am open to any suggestions that might come my way. Never a dull moment in HotRod Land. Mike

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/20/22 at 22:45:23 Oooooooops!  I missed the intake port epoxy.  The crack is pretty big now.  It hasn’t failed but it certainly deserves attention.  You can really see the crack.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/20/22 at 22:47:13 The edge of the epoxy is also starting to show signs of separation.  What the heck, after over 22,000 miles I think it served me well.  I have to remove the valves to resurface the valve tips so now is a good time to renew the epoxy.  I’ll have to throw it back on the flow bench to make sure I get it right.   That will be fun.  My wife hates all the noise, but I will figure out a way to make it up to her.  She’s the best. Will also have to repair that 8mm head stud with the special upside-down insert.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by justin_o_guy2 on 10/21/22 at 14:08:50 If you're piling epoxy deep, you might want to use Rebar. If it is gonna be deep, I like layers. Press the first application onto the metal. Wet it. Wet it Good! ( Lyrics of an old song?), then continue to apply, let it cure,break the surface, get rid of all of it, and leave foot Tooth. Use forty grit, or meaner, Wet That, wet it good! Rinse,repeat. Considering all the things trying to bust it up, maybe some fine Hobby wire for rebar? Hobby shops that sell RC airplane stuff keep, what I call, piano wire. But without any lumps and bumps like rebar has, IDK how helpful it would be. I put bondo on a Mack cabover, on the eyebrow over a headlight. Beat the flux offa coupla welding rods, and filled about an inch and a half dent. It survived the heat and cold of West Texas and the punishment of the oilfield roads for about five years without cracking. They retired the truck and that ended That experiment. What is the max depth of your epoxy? https://acrylgiessen.com/en/high-temperature-epoxy/#:~:text=High%20heat%20epoxy%2C%20on%20the%20other%20hand%2C%20is,which%20enables%20the%20epoxy%20to%20withstand%20high%20temperatures. https://acrylgiessen.com/en/high-temperature-epoxy/#:~:text=High%20heat%20epoxy%2C%20on%20the%20other%20hand%2C%20is,which%20enables%20the%20epoxy%20to%20withstand%20high%20temperatures. I know you're a lot better mechanic than I'm ever gonna be, I'm just trying to help.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by TheSneeze on 10/21/22 at 16:02:22 My 4 speed motor was in a bike that showed 9800+ miles on it.  Absolutely no other info or history.  You previously asked me to inspect the gears for pitting.  Not a one.  They look clean.  Enough so that I am not going to split the cases.  Well, I guess I should measure the crank play and run out before I say that with too much conviction.  I have 95% of what I need to reassemble this hot rod engine, but I am saddled with too many projects lately.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 10/21/22 at 19:58:34 JOG, thanks for the tip on the Stone Coat.  I'll look into it.  I doubt that I will switch from the JB Weld High Heat putty.  I'm having excellent results with it, and because it's a two-part log the consistency is perfect for the initial application into the port.  I would be very reluctant to put any sort of metallic reinforcement into the epoxy.  If piano wire or stainless mesh got loose and went through the valves it would be horrific. Thanks for refreshing my memory Sneezy.  Sure wish you had told me that your gearset was installed in a maximum effort motor that had been run on a flat track for an entire race season.   I spent a couple of hours putting around on the 4-speed this morning.  I'll get used to it.  It actually shifts better than the 5-speed.  But the absence of the extra gear keeps me wishin it was still there.  I guess I got spoiled.  One nice feature is I always know when I'm in top gear.  With the 5-speed, I was always checkin to make sure I was in top gear. C'mon gang.  I know there must be some of you with engines on the deckplates all opened up.  Take a peek in there and see if ya gots any pits in them gears.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by justin_o_guy2 on 10/21/22 at 20:46:09 If piano wire or stainless mesh got loose and went through the valves it would be horrific. Well, yess indeedee it would.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by Moarpower on 10/23/22 at 16:45:01 Aweseome posts and I will read through a few times. I am pulling out my 87 engine today as I have some noise and aluminium in the filter. I have decided not to sell it and keep it for another couple of years. I am going to buy Lancers stage 3 cam if the 2 way shipping cost isn't going to make it too expensive. I am going to go up to a 97mm Wiseco as I have found a few people with them here in Australia for sale. Will need to inspect the top end and valves for wear and decide what else I need to replace to freshen up this motor. It currently has the stock carb with 155 and 55 jets, straight pipe and a cone filter.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 11/13/22 at 17:29:32 After my last post on 10/21/22, I moved on to my next project, the Big Bore 4-Speed.  That engine is in the bike now and I’ve been breaking it in.  It runs good.  Hope the 4-Speed gears can hack the mission.  In between rides, I’ve been tearing down this 94mm flat-top engine and have noted a few things that should be of interest. I mentioned that my compression pressure had dropped to about 205 psi.  Although the engine ran perfect, was quiet, and had loads of power, the oil consumption was high.  The high oil consumption and reduced compression pressure warranted a closer look at the rings and piston.  I had already checked the valves and they weren’t leaking. I noticed that on the exhaust side of the piston there appeared to be carbon tracks from ring blowby.  See the carbon between the 2nd groove and the oil control groove.  I’ve never paid much attention to this before.  Looks like a very informative inspection point.  I’m gonna start lookin at this area in the future.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 11/13/22 at 17:30:18 The rear side of the piston isn’t as bad as the front.  Only trace amounts of carbon accumulation below the 2nd ring groove.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 11/13/22 at 17:31:01 I reviewed my old files and noted that at the 2250 mile teardown there was zero evidence of blowby on the front of the piston.  So, the blowby problem developed as the miles racked up, or possibly I managed to bugger up a ring when I reinstalled the jug.  However, visual inspection of the rings didn’t reveal any sort of damage. Here’s what things looked like at 2250 miles.  Clean, no blowby.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 11/13/22 at 17:32:16 I checked the ring free gap.  Both the top ring and the 2nd ring had free gaps right at 11mm.    The factory wear limit is 9mm & 11mm respectively (note: bigger is better), but that’s for factory rings.  Comparing the used Wiseco rings to new Wiseco rings seemed prudent.  I have a set of brand-new rings and the free gaps were 12mm & 13mm.  The old rings didn’t seem too far off the mark.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 11/13/22 at 17:32:57 Ring end gaps were .026” for the top ring, and .029” for the second ring.  When I originally gapped the rings, the gaps were .024” and .028” respectively.  So, there wasn’t much wear.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 11/13/22 at 17:33:40 I had measured the piston and compared it to the detailed drawing.  The detailed drawing specifies 3.6985”, and the piston measured 3.6985”.  I slipped the piston into the cylinder and checked clearance with a feeler gage (quick & dirty).  It was .005”.  That seemed like a lot.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 11/13/22 at 17:34:34 I reviewed my assembly notes and the notes said that the piston was 3.7005” when I installed it, and the clearance was “a loose .003””.  Hmmmmm?  That explains the additional .002” clearance, but I’m confused regarding the piston size.  Is it possible that the drawing spec of 3.6985” is a target dimension?  Sort of like a desired diameter after the sharp tool points are worn off.  IDK.  All I can do is speculate.  I don’t think I was careless with my measuring at initial assembly.  Probably would have been good if I had dug into this at the initial teardown (2250 miles).  The .005” clearance isn’t conducive to good ring seal.  I’m sure the excessive clearance doesn’t help, but what the heck, it was runnin great when I tore it down. My notes from 10/27/20 show that I measured the brand-new piston at 3.7005”.  So, the fact that it is now 3.6985” indicates that it must have worn .0020”.  The original installation clearance measurement was a loose .003”, so it looks like skirt-wear to me.  Originally .003”, now .005”, so clearance increased .002”.  Makes sense.  Wiseco drawing WD-12514 specifies a major diameter of 3.6985” which is what I have now, so looks like they might make the slug slightly oversize using a phonographic finish and then intend for about .002” break-in wear.  The crests of the tool marks wear in.  The tool marks hold oil for the break in and also limit friction since only the crests contact the cylinder wall.  If I were to get a brand new piston, I’m bettin it might be about .002” bigger. Hey Lancer, could you measure one of those new 94mm flat-tops and tell me if it’s 3.7005” or 3.6985”?

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 11/13/22 at 17:37:39 So, the rings looked good, and the valves checked out.  There was no evidence of a head gasket leak.  The only thing I can see that might be the cause of the reduced compression would be the bore and/or the skirt clearance.  Those linear marks probably result in some leakage.  Looks like debris off the gear teeth strikes again.  The piston rocking in the bore most likely results in some leakage too. Another possibility could be my compression gage.  As of late, I seem to be seeing 200 to 205 psi an awful lot.  I have also noticed that it doesn’t seem to hold solid at the max achieved pressure.  It tends to bleed a bit and then holds.  I need to check out the gage. This thing was runnin great when I tore it down.  Aside from a bit of oil consumption, all was good.  Power, noise, vibration, temps, pressure were all good.  I’m sure I could have continued to run it for a good long time.  I’ve been reading a lot about gear pitting.  Gears have a tendency to pit in areas where there is heavy contact, and then as the load gets redistributed across the tooth the pitting subsides.  The gear gurus refer to this as “initial pitting”, as opposed to “destructive pitting” (self-explanatory).  My pitting doesn’t look like initial pitting, but who knows. I have the bottom end completely disassembled.  With the exception of 4th gear, all looks good.  I plan to figure out a way to provide more lubrication to the two top gears (4th & 5th on a 5-speed, or 3rd & 4th on a 4-speed).  That should prove challenging.  While I’m figuring that out, I will continue racking up the miles on the Big Bore 4-speed.  I have a way to monitor the gears for pitting.  If I don’t detect any pitting, I will run it at least 10,000 miles before I tamper with it.  I want to see if the heavier 4-speed gears hold up better than the 5-speed gears. More to come.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by LANCER on 11/13/22 at 18:21:23 Hey Lancer, could you measure one of those new 94mm flat-tops and tell me if it’s 3.7005” or 3.6985”? I measured 3 pistons: 3.6805” 3.6775” 3.6795”

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by Armen on 11/13/22 at 22:28:25 So, this begs the question-what is your assembly/break in procedure for the piston/rings? In the 70’s, when Udo Gietl was building F1 and then Superbike BMWs, he ran into all sorts of grief with ring seating. Big ass air-cooled motor. After a ton of work, he came up with the following routine, which I still use: After the cylinder is honed (bead hone), thoroughly wash the cylinder with hot soapy water, and dry. Do not put any oil on the cylinder walls, not even WD-40. Assemble the rings on the pistons, install the piston in the cylinder just up to the bottom of the rings. Put one dot of oil on the piston skirt front and back. Complete assembly. Use a break-in oil in the motor. Regular amount of oil. Non-synthetic, like the basic Honda oil or the Amsoil break-in oil. 10-40 or thinner. Put a fan in front of the motor. Start the bike and hold he revs to about 2K. Run for 30 seconds or so until the smoke stops. Hop on the bike and ride. Not lugging, not redlining. Varying throttle. Do this for at least 100 miles without excessive idling. Once the bike has 300 miles, dump the oil and use your regular oil. I’ve pulled apart lots of motors that I’ve broken in this way, and always saw almost complete contact/wear on the middle ring, and no blow by past the middle ring. Minimal blow by past the top ring.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by TheSneeze on 11/14/22 at 08:17:06 I had my cylinder bored and rings gapped at the shop that did my porting.  He gaged the bore diameter off the piston, and then gapped the rings to the new bore.  I haven't checked any sizes yet to see what clearances he used.  He came from Thumper Racing that specialized in big bore singles.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 11/14/22 at 12:03:31 Lancer, thanks very much for taking the time to check the piston size.  I think maybe you measured in the wrong location or possibly are misinterpreting your thimble.  The reedings you provided would result in a clearance on the order of .020" (0.5 mm), which is astronomically big. I measure my piston at a location 1/2" up from the bottom of the skirt, and 90 degrees from the wrist pin bore.  Like this.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 11/14/22 at 12:12:08 I know the factory manual specifies a location 20mm up from the bottom of the skirt, but that's for a cast piston with a full skirt.  On the Wiseco, I noted that at the 20mm location the piston was about .0005" smaller in diameter, but nothing close to the measurements you provided. I'm fairly confident in my readings.  I have a Starett micrometer so it's good quality, and it checks out when I put it on the 3.000" standard.  It doesn't have a vernier but I'm pretty good at interpolation.  Can you take another look?

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 11/14/22 at 12:59:50 Armen, I do a standard break-in with petroleum oil, usually Rotella T4 or Castrol V-Twin 20W-50.  Depending on the project, I break it in for about 200 to 1000 miles.  This 94mm flat-top got a 500 mile break-in. Some habits are hard to kick.  I spent a lot of time fiddling with drag bikes.  You don't have the luxury of a lengthy break-in period.  I have been finishing the cylinders with a 180 grit hone with a brief touch up with a 280 grit.  The intent is to leave the surface a bit rougher than generally accepted practice so the rings seat ASAP.  I don't skimp on assembly lube.  So that's the finishing process I used on this particular engine.  It seemed to be working just fine at the 2250-mile mark when I first tore it down to start the Evolution of a Hotrod project.  It didn't start consuming oil until I reassembled it to continue testing.  When I reassembled it, it went back together as-is, no honing, no new rings.  That might have been a problem. My breakin regimen is fairly simple, while it's on the dinosaur oil diet, I use a constant accelerate/decelerate technique.  Open throttle to accelerate which forces the rings into the cylinder wall, then chop the throttle to decelerate, pull vacuum in the cylinder, and draw oil up the cross-hatch.  That goes on for the entire breakin period.  Anyone that is following me doesn't stay there very long.  The constant change in speed drives them nuts.  It's easy-does-it for about the first hundred miles, and then gradually increasing power until it reaches my desired finish point.  On this engine, that was 500 miles. I'm not too concerned about the oil consumption.  It was minimal and didn't seem to start until I reassembled the engine without changing the rings or honing the cylinder.   I can tell you that on my current test mule (97mm bore pop-top), I changed my cylinder finishing process.  That change was not related to any sort of issues I noted on this 94mm flat-top engine.  I wanted to try and get my bore as round and straight as possible, set the running clearance right at .0025", and try a smoother finish.  So, after boring the cylinder (.006" under finished size), I got it within .003" with 80 grit and 180 grit, then took out the last .003" with the 280 grit stones.  That last .003" took a long time.  My back was killin me, but I was very happy with the finished product.  We'll have to see how it works out.  So far, oil consumption is zero.  My breakin was 1000 miles. I really feel that the blowby I'm seeing on this particular piston is related to debris.  While the linear marks in my cylinder appear superficial, the fact that I can see them tells me they aren't superficial.  The marks are mostly on the forward side of the cylinder wall, and that's where I see the blowby.  A steady diet of gear-tooth fragments takes a toll, but as previously mentioned, it was still runnin great when I tore it down. There was no obvious loss of performance, but the squeeze was down a bit.

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 11/14/22 at 13:04:09 Sneezy, I'm confused.  I thought you have a 94mm piston.  There shouldn't be any boring or sizing involved.  Your used bore would have already been a bit larger than desired.  The machinist would have been trying to achieve a good finish for the rings without making the bore too large.  Do you have a 94mm or a 97mm?

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by TheSneeze on 11/14/22 at 13:16:17 Apparently I am, too.  Yes, you are right...  a 94mm piston, and the cylinder wall was honed for a clean up.  I am in the middle of three engine rebuilds right now, thus the confusion.  Currently starting the break in on a Kawasaki KZ750 as well.  I guess my brain is still trying to keep up... LS650 hot rod motor EJ25 Subaru sohc n/a 5.2l Magnum V8 Mopar

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by LANCER on 11/15/22 at 10:28:25 25232C50525551610 wrote: Lancer, thanks very much for taking the time to check the piston size.  I think maybe you measured in the wrong location or possibly are misinterpreting your thimble.  The reedings you provided would result in a clearance on the order of .020" (0.5 mm), which is astronomically big. I measure my piston at a location 1/2" up from the bottom of the skirt, and 90 degrees from the wrist pin bore.  Like this. New measure taken 3 times: 3.7005”

Title: Re: Wiseco Flat Top Piston - Installation & Test Post by DragBikeMike on 11/18/22 at 10:19:16 Hey Lancer, thanks very much for checking that measurement again.  I feel a little better now.

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