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Message started by DragBikeMike on 07/15/21 at 16:20:55

Title: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 16:20:55

This is the fifth in a series of reports intended to document the results of progressive modifications to the LS650 engine.

Part 1 outlined the project, set the rules, and established the baseline performance values for a box-stock LS650. You can find Part 1 here.

http://suzukisavage.com/cgi-bin/YaBB.pl?num=1620523526

Part 2 examined the airbox. We improved performance dramatically with a few simple and inexpensive modifications. It was a lot of bang for the bucks. You can find Part 2 here.

http://suzukisavage.com/cgi-bin/YaBB.pl?num=1621150483

Part 3 took a hard look at the exhaust system. We tried a Dyna muffler and a hybrid muffler that I manufactured. We also tried the larger Mac header pipe. The exhaust modifications provided significant improvements in acceleration and fuel economy. You can find Part 3 here.

http://suzukisavage.com/cgi-bin/YaBB.pl?num=1623048749

Part 4 installed a performance carburetor and revisited the air filter. You can find Part 4 here.

http://suzukisavage.com/cgi-bin/YaBB.pl?num=1625732492

Part 5 installs a new camshaft with higher lift and duration. The results were gratifying and informative. With some valve overlap, the exhaust header takes on a new role.

What I am about to describe worked good for me. If you decide to try this stuff on your own, you assume responsibility for the outcome. If you don’t have the skills, don’t do it. If you don’t understand something, STOP and get help. Get a manual. Read up. Comply with ALL the safety requirements outlined in the manual. Make sure you know what you are doing before attempting any of these modifications.

Let’s get started.

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 16:22:12

At the completion of Part 4, we had plucked all the low hanging fruit, the easy and relatively inexpensive stuff. Now it’s time to dive into the engine. The intake and exhaust systems have been optimized to increase airflow into and out of the engine, but there is a set of valves in between the intake and exhaust systems. Those valves start & stop flow through the combustion chamber. The camshaft controls when the valves open and close, and how far the valves open. Valve timing and lift have a big impact on airflow through the engine, maximum power, and what rpm the maximum power is achieved.

We will be installing a new camshaft. The replacement cam is an OEM part intended for the early model DR650 (1990 – 1995). Full disclosure, the cam you see in this report is a well-used DR650 cam.

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 16:23:04

The DR650 cam is a good choice for several reasons.

1. It’s an off the shelf part available at the local Suzuki dealer or any of the on-line parts suppliers (Partzilla, Babbitt’s Suzuki Parts House, Ron Ayers, BikeBandit, etc.).

2. It’s a bolt-in cam. It doesn’t require a special set of springs, machining valve guides, notching the piston, etc. It simply bolts right in, a direct replacement for the stock LS cam.

3. It provides more duration, more lift, and some valve overlap. Valve timing is close to the Stage 3 cam Lancer sells.

4. It’s a brand-new cam, not a refurbished cam, so no core charge is involved. The journals are pristine, and you keep your original stock cam.

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 16:23:39

Compared to the stock LS650 camshaft, the DR cam has more lift, more duration, and some valve overlap.

Seems like every manufacturer uses a different method to measure timing. The Society of Automotive Engineers uses the exact point where the valve moves off the seat. Most cam manufacturers use an arbitrary value (.020”, .040” or .050”) at the lobe. Some cam grinders (like Webb) use an arbitrary value (.050”) at the valve. It’s tricky to compare one cam to another. For this report, I provide tables that show timing data measured at .020”, .040” and .050” at the cam lobe, and timing curves that show exactly where the valves are throughout 720° of crankshaft rotation. There should be enough data to permit accurate comparison to other cams (apples to apples so to speak).

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 16:24:32

The stock LS650 camshaft works OK considering it is a short-duration low-lift bumpstick. It has zero valve overlap. Overlap comes in handy. It provides an avenue for inertia developed in the moving gasses to scavenge and fill the cylinder. On a naturally aspirated engine, valve overlap makes it possible to achieve volumetric efficiency approaching, and sometimes exceeding, 100%. Without valve overlap, you would need a turbocharger or supercharger to exceed 100% volumetric efficiency.

The table below provides timing and lift data that I took on a stock cam. You can see that at any of the usual arbitrary lobe lifts (.020”, .040” or .050”) there is zero overlap. If you look at the valve lift at top dead center (TDC), you can see the valves are barely open (.018” intake, .032” exhaust). Not much air is gonna squeeze past a valve that’s only open .018”.

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 16:25:03

The DR650 cam is a bit spicier. It has about .020” more lift, about 20° more duration, and a spoonful of valve overlap to zip things up. At TDC, the valves are open enough to allow some flow, but they aren’t open so far that you have to worry about interference with the piston. Now the inertia developed in the rapidly exiting exhaust gas can help pull a fresh intake charge into the combustion chamber.

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 16:25:50

This is a graph of the intake curves for the two cams. You can see that the DR cam opens the valve sooner and lifts it higher but closes the valve just a bit earlier than the stock cam. Closing the intake valve a bit sooner can improve low speed torque, but it can also cause problems with detonation. The DR cam has significantly more area under the curve than the stock cam has.

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 16:26:33

This is a graph of the exhaust curves for the two cams. The DR cam opens the valve earlier, lifts it higher, and closes the valve later. The opening event is just a few degrees earlier than the stock cam. If you open the exhaust valve too early, you diminish low speed torque. Again, the DR cam has significantly more area under the bell curve than the stock cam has.

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 16:27:16

A visual comparison of the intake lobes should give you an idea how the two cams achieve different valve timing and lift. The stock cam is on the left, the DR cam is on the right.

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 16:28:05

One significant difference between the two cams pertains to lubrication. The stock cam has holes drilled in the lobes to provide additional oil between the cam lobe and rocker arm. The DR cam does not have these oil holes. Stock on left, DR on right.

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 16:29:00

It appears that the lion’s share of lubrication is derived from the lobe dipping into the oil trough just below the cam. As the cam rotates, the lobes dip into the reservoir of oil.

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 16:30:12

I have run the DR cam without the oil holes for about 4500 miles with no ill effects. However, if you prefer the stock oiling arrangement, you can drill oil holes in the lobes. I believe Dave did a nice post specifically on drilling these holes. You can also find the drilling specifics in this old post, but it might be a lot of reading.

http://suzukisavage.com/cgi-bin/YaBB.pl?num=1596951230

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 16:31:10

Changing the camshaft is not too difficult, but it does require an understanding of how to correctly set the timing. If you don’t correctly time the cam, you run a good chance of wrecking your engine. Get the manual. Read up. Understand what you are doing. This post just hits on the highlights.

To get to the cam, you have to remove the head cover. Rotate the engine to top dead center on the compression stroke. Verify it’s on the compression stroke by checking that the intake and exhaust rocker arms have play.

Remove the fuel tank, decompression solenoid, breather hose, top engine mounts, carburetor, etc. It should look like this, as much room as possible over the top of the head cover.

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 16:31:55

Another picture of how things should look from the right side of the motorcycle.

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 16:33:05

If you are working on an older LS with the “old style” rocker arms, I suggest you upgrade to the newer style rocker arms (12840-24B10 Intake, 12850-24B10 Exhaust). You really don’t want to run your brand-new cam with a set of old, chewed-up rockers. Replacement will require removal of the intake rocker shaft plug. Best break it loose now while the head cover is anchored to the engine.

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 16:33:49

The “old-style” rocker arms do not have hardened cam follower pads, and the arm itself is not as robust. This shows the old-style vs the new-style (old on top, new on bottom). Note the special hardened cam follower pad. It’s brazed to the rocker arm. Much better. Also note the additional material used to reinforce the body of the rocker arm.

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 16:34:28

Another view from the underside. Old-style on top, new-style on bottom.

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 16:36:19

Remove the bolts that secure the head cover to the cylinder head. These bolts seem to be a problem for many Savage wrench turners. There’s a lot of them (16 or so), all different lengths, some with sealing washers, and some without sealing washers. They are easy to get mixed up.

The Clymer manual and factory service manual both have nice illustrations that show exactly where all the bolts and sealing washer go. Pay attention to the illustration. If you mix up these fasteners, there’s a good chance you will either strip out the internal threads in the aluminum, or break off a bolt. Some folks make a nice big copy of that illustration and poke holes in it to accommodate each bolt. It helps to keep track of things.

Carefully take the head cover off and set it aside.

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 16:37:44

Now you can see the cam. Note the position of the cam lobes. They point down into the reservoir full of oil. I refer to that reservoir as the “trough”. When the head cover goes back on, this is ho the cam lobes must be oriented, facing down into the trough.

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 16:38:52

To remove the cam shaft, you must loosen the cam chain. Only way to do that is to remove the cam chain tensioner. So, remove the header pipe and the clutch cover.

To prevent losing any small parts in the engine, it’s a good idea to place a clean paper towel in the openings below the clutch.

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 16:39:56

To prevent leaving any sort of cleanliness towel behind, and to remind you to do a thorough inspection before reinstalling the clutch cover, it is a good idea to put a zip tie in one of the clutch cover bolt holes, sort of like a red tag (only grey, or black, or white, or whatever color your zip ties are). I know a guy who failed to do this.

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 16:41:00

Remove the circlip that secures the tensioner at the rear.

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 16:42:13

Remove the bolt that fastens the tensioner to the cam chain guide. Make sure you hold the nut that’s attached to the guide. Use a wrench on the nut as shown. If you don’t hold that nut, you may break the guide. Don’t try and turn the bolt until you have a wrench on the nut, as shown.

BTW, that chain tensioner is gonna try to fly apart when you remove the bolt. There’s a spring inside.

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 16:43:18

Now the cam chain will be loose. Bend the lock tabs on the cam sprocket bolts and remove the bolts. You will have to rotate the engine to access both bolts. No problem, the rocker arms have been removed so there is no concern over running a valve into the piston.

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 16:44:45

Use a small screwdriver or rod to gently push the thrust ring out of its groove. Key words & phrases, “gently push”. No beating, driving, prying. A gentle push should be all that’s required to get it started, then just roll it on out.

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 16:45:25

Now the cam can be shifted to the left. Slip the sprocket and chain to the right and pull out the cam. Watch out for the drive pin, don’t lose it.

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 16:46:23

Clean out the oil trough and inspect the cam bearings. Clean all the old sealant off the head and head cover. Inspect the head plug to make sure it is not loose. Now is a good time for one of those special Verslagen plugs.

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 16:47:45

Inspect the valve stem tips. You want nice circular wear patterns, no chipping or galling. Make sure the spring retainers are not cocked and the cotters are seated. Check all four valves.

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 16:48:42

There are timing marks on the right-side of the cam shaft.

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 16:49:28

There is a timing mark (TDC mark) on the end of the alternator rotor.

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 16:50:10

And a timing mark (notch) in the alternator cover.

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 16:50:59

Set the crankshaft at TDC by lining up the marks on the alternator rotor and alternator cover.

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 16:52:17

Install the DR cam. Don’t forget that drive pin. Apply some assembly lube to the cam journals and install the cam, cam sprocket, and cam chain. It’s a juggling act. No need to force anything. No worries about running a valve into a piston, the rockers aren’t installed yet. You have to keep fiddling around with it until you achieve a condition where the TDC marks on the alternator rotor and alternator cover are lined up, and the timing marks on the cam align with the head surface, all at the same time. I like to use a six-inch scale to get it exactly right. Install one cam sprocket bolt finger tight to hold everything together.

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 16:53:16

Use your finger to push on the rear chain guide and take up all the chain slack. Rotate the engine through several revolutions and check that each time the TDC marks align on the alternator, the cam timing marks align with the head surface. Once you are confident that the timing is correct, install the chain tensioner.

I like to use this little tool to lock the tensioner in the fully retracted position. You can also use a zip tie as described in the all-inclusive Clymer manual.

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 16:54:02

Retract & lock the tensioner like this.

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 16:54:51

Slip it over the pin and then connect it to the chain guide with the special bolt. Apply red Loctite to the bolt. You really don’t want that bolt coming out.

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 16:55:36

Again, when you tighten the tensioner bolt you MUST hold the nut on the chain guide with a wrench. If you don’t hold the nut, you might break the guide.

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 16:56:31

Install the circlip on the pin. Make sure it seats in the groove.

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 16:57:32

Now you can release the tensioner by pulling out the plastic locking device. Don’t skip this step.

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 16:58:18

Rotate the engine through at least four complete revolutions. After each revolution, stop at TDC and make sure all the marks line up. The marks on the cam MUST align with the head surface when the marks on the alternator rotor and cover line up. I strongly advise you perform this quadruple check, just to be sure.

Once you are sure the cam timing is correct, you can permanently install the cam sprocket. Use red Loctite on the cam sprocket bolts along with a new lock tab plate. Re-using the old plate is not worth the risk. Install the thrust ring in the groove.

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 16:59:08

The lock plate can go on two ways. Install it as shown, covering the drive pin. You want it to cover the drive pin so that the pin is captured. See the pin just peeking out over the edge of the plate. Also note that when you install the head cover, the drive pin must be in this position (1 o-clock) so that the cam lobes are pointing down into the oil trough.

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 16:59:57

Vice grips work great to fold the lock tab over the flats on the bolts.

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 17:00:35

Now is a good time to capture and record a little data. Measure the cam chain tensioner extension and record the value. Then, when you open the clutch cover again you can keep track of the extension. Mine is on the high side (16.5mm). I checked with Versy just before I closed it up to get a feel for the drop-dead point. He said 18mm was the magic number. I think I can probably run this baby long enough to finish up the project.

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 17:01:26

Since the clutch cover is off, might as well check the primary drive nut and the balance shaft bolt. Use soft copper to lock the drive gears and verify that the primary nut (left-hand threads) is torqued to 75 ft-lbs. and the balance shaft bolt (right-hand threads) is torqued to 35 ft-lbs.

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 17:02:06

Here you see the soft copper placed between the drive gears. Soft rolled copper tubing works great.

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 17:02:43

Better to mangle the copper than to mangle the gears. I’ve done this dozens of times and haven’t put a mark on a tooth yet.

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 17:03:22

Never mind trying to use a rattle wrench on the primary drive gear. Torque wrench only for this job. You don’t wanna end up with one of these. That would be the unofficial inspection port for rod bearing inspection.

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 17:04:13

This is the balance shaft bolt. Same guidance, torque wrench only. Don’t exceed 35 ft-lbs.

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 17:05:06

If you are changing rocker arms, install them in the head cover. Assembly lube is in order. The wave washers on the right side of each rocker arm can be a real pain in the keester. They get caught on the edge of the hole, so you can’t move the washer into correct alignment. I find that a couple of shims or feeler gages (.006” to .008”) make the job a lot easier. Sandwich the wave washer between the feeler gages/shims. Then, when the washer is in the correct location, pull out the feeler closest to the rocker arm while holding the washer in position. Then, gently push on the shaft while you remove the outer feeler gage.

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 17:06:05

Make sure all the sealing surfaces are pristine, free of any oil or old sealant. Do a quick inspection to make sure you haven’t forgotten anything. Apply some assembly lube to the cam lobes, the rocker pads, and the valve tips. Keep the lube away from the sealing surfaces. Make sure the plug/cap on the right side of the camshaft is in place.

This plug. The one you can see on the right side when the head cover is installed.

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 17:06:54

You must install the 70mm bolt with sealing washer in the location shown before you put the head cover on the engine. As you can see, the frame is in the way. You won’t be able to install the bolt once the head cover is on.

This is the 70mm bolt in question. It must be in place before you install the head cover.

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 17:08:18

Installing the head cover is a delicate operation, and you don’t want to screw up the layer of sealant by dragging it across other stuff. It helps to do several dry runs to figure out the best path to follow, then apply the sealant and do the final fit when you are comfy with the operation.

This is how your sealant should look. An exceedingly thin layer. Keep it away from the edges of the cam bearings. Make sure the oil separator screen is in the breather cavity.

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 17:09:17

Remember, this is how your cam should look before installing the head cover. The lobes must be pointing down into the oil trough, not up. Make sure the thrust ring is in the groove properly.

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 17:09:54

Once the head cover has been installed and the fasteners tightened properly, adjust the valves. I set mine to .005”.

Reinstall the clutch cover with a new oil filter. Don’t forget to remove any cleanliness barriers. Check closely to make sure everything is in order. Here’s where that red-tag zip tie comes into play. BTW, don’t forget to remove the red-tag zip tie.

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 17:10:38

Use an oil can to fill the cam trough with clean engine oil. Pump the oil through the intake valve access. Use a hose to direct the oil straight into the trough.

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 17:11:58

If you have a connection for an oil pressure gage, attach the oil can and fill the trough through the gage connection. It works good. You can watch through the intake valve access. Keep pumping until the trough fills up and spills over.

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 17:12:44

Fill this trough (reservoir), not the entire cylinder head cavity.

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 17:13:33

Reassemble the motorcycle. Install the decompression solenoid, top motor mounts, carburetor, breather hose, fuel tank, seat, exhaust header, and anything else you removed.

Fill the crankcase with good quality oil. Motorcycle oil (10W-40 or 20W-50) rated API-SG is a good choice. Ready to fire up.

A quick compression check showed that the cranking pressure was still the same, 160 psig. The early closing intake valve had zero impact on cranking pressure.

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 17:16:11

It started right up. Took a few seconds to develop oil pressure and settled into a slow idle. It took an additional ¾ turn on the idle stop to achieve a satisfactory idle. That was the only adjustment necessary to make it rideable.

No break-in required on this installation. The cam and rockers already had about 4500 miles on them. I keep them together, as a matched set. So, it was time to get down to business.

Power delivery felt excellent. It has a little bit of a hit now (right about 3500 rpm) but still plenty of torque at lower rpm. The top end is extended significantly. It buries the tach (8K) in first and second gear, and pulls all the way to 7450 in third gear. It really should have a rev limiter.

Once I was sure it wasn’t too lean, I started doing timed pulls. It didn’t disappoint. Let’s look at the setup. Stock engine with DR 650 cam, stock cylinder head, stock piston, stock bore & stroke, stock compression ratio (8.5:1), modified airbox with K&N RD-0710 cylindrical filter element, PWK38 carb, stock exhaust header, LCGP high flow muffler.

It was time to see how it did against the stopwatch. I achieved best performance with a #35 pilot jet, #145 main jet, and the needle clip in the fourth groove (rich).

Second Gear 4K to 7K: 2.97 seconds 0.27 seconds faster than stock cam

Third Gear 4K to 6.5K: 5.24 seconds 0.53 seconds faster than stock cam

Third Gear 4K to 7K: 7.65 seconds 1.20 seconds faster than stock cam

Fifth Gear 3.5K to 5K: 5.02 seconds 0.63 seconds faster than stock cam

Fifth Gear 3.5K to 5.5K: 7.75 seconds 0.95 seconds faster than stock cam

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 17:22:10

Time to try it with the Mac header. The bigger header wanted less fuel. I achieved best performance with a #35 pilot jet, #142 main jet, and the needle clip in the fourth groove (rich).

Second Gear 4K to 7K: 3.00 seconds 0.03 seconds slower than stock header

Third Gear 4K to 6.5K: 5.49 seconds 0.25 seconds slower than stock header

Third Gear 4K to 7K: 7.80 seconds 0.15 seconds slower than stock header

Fifth Gear 3.5K to 5K: 5.43 seconds 0.41 seconds slower than stock header

Fifth Gear 3.5K to 5.5K: 8.42 seconds 0.67 seconds slower than stock header

It pulled 7500 rpm in third gear (50-rpm increase). Based on the acceleration times, it’s obvious that the larger header is a bit slower. Before the cam change, the larger header was faster. Why is that?

The short answer, valve overlap. Now that both valves are open at TDC, the inertia of the hot gas moving out the exhaust system can help evacuate the cylinder, and help pull in a fresh charge through the intake. A body in motion wants to stay in motion. A column of hot exhaust gas is a body too, it has mass.

Although the larger exhaust pipe is less restrictive, the hot exhaust gas moves at a lower velocity. Lower velocity, less inertia, less pull. At this stage of modification, the smaller stock header works a bit better than the larger Mac header.

If you review Part 4, you will see that when the stock cam was in play, the Mac header performed better than the stock header. That setup took advantage of the reduced restriction afforded by the larger pipe. The engine didn’t care much about the inertia of the exhaust gas because both valves were essentially closed during the overlap period. There was no overlap.

Don’t get the wrong idea here. Both setups are plenty fast. You would be hard pressed to tell the difference between the two pipes. They both feel great with the DR cam. When subjected to the scrutiny of the stopwatch, the stock pipe is just a bit faster.

It would be great if I had a 1.5” and a 1.62” header pipe to test along with the stock 1.3” and Mac 1.79”. Hey, a header shootout. Who’s got pipes to share?

Moving forward, it will be interesting to see what happens when we install the ported cylinder head with the 1.5” diameter exhaust port. Will the tables turn? Will the Mac pipe work better with the larger port? What will happen when we bump up the compression ratio? Which pipe will work better with 10.5:1 CR? Which will work better with more displacement? This project is a kick, I’m lovin it. Build it up piece by piece and test each piece as you go.

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 17:23:14

A cam installation wouldn’t be complete without a fuel economy test. With the stock header, she went 54.7 miles on a gallon of 89 octane E-10. With the Mac header it squeezed 55.6 miles out of a gallon. I think that’s a wash. The cam hasn’t had any effect on fuel economy.

Temperatures are the same. Cruising on the freeway, oil temp is around 210°F and cylinder head temp (CHT) is around 310°F. The cam doesn’t affect the temps.

Oil pressure is up slightly. It runs 1.0 to 1.5 psig higher under all conditions (temp & rpm). Seems logical, fewer holes = higher pressure.

The exhaust valve timing doesn’t seem to affect noise very much. Using my iPad with the NIOSH app, the noise levels at 1300/3000/4000 rpm are 68/78/80 dB. Looks like opening the exhaust valve 6° earlier raises the noise level about 1 dB. I can live with that. It’s still pretty quiet.

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by DragBikeMike on 07/15/21 at 17:25:46

This completes the cam shaft portion of the project. The DR650 cam worked great. It was easy to install, a true bolt-in. No machining, no special tools.

Let’s take a look at the results using test data from the stock header setup (keeping the project simple & cheap). The setup includes a mostly stock engine, stock bore & stroke, stock compression ratio, stock cylinder head & valves, stock header pipe. We have installed a DR650 cam ($230 or $366 with rockers), PWK38 carb ($28), K&N RD-0710 air filter ($40), modified airbox, catch can ($20), and LCGP 2.5” resonator with baffle ($100).

We have improved the overall performance of the motorcycle. Carburetion is excellent but fuel economy is not as good as we achieved with the stock carburetor. Backfiring has been eliminated. Audible noise has increased a modest amount, but the quality of the exhaust note is more pleasing to the ear. Compared to the box-stock motorcycle, third gear acceleration has improved by 5.24 seconds, and fifth gear passing acceleration has improved by 4.45 seconds (14.68 seconds if you run it all the way up to 5500 rpm). It’s got some muscle now.

That’s pretty good, but the price tag is starting to creep up. The DR cam will set you back about $230 bucks, and if you opt for new rocker arms you can add an additional $136 to the tab. We’ve done some minor work on the engine that required a good understanding of cam timing. Most of us could accomplish these simple modifications for under $560 bucks. The tests show that in this state of tune it runs a bit better with the stock header.

Now it’s time to break out some special tools. Next stop on the Power Train? Flywheel. Let’s see what happens when we lob off some of that rotating mass. Part 6 will install a three-inch flywheel.

At this point, I have done 171 WOT acceleration pulls to dial in the different combinations. There’s a little over 2400 miles on the engine since it was restored to box-stock configuration. The old girl is still holdin up good. No leaks. No ugly noises. Not using any oil. Just a bit of oil accumulating in the catch-can (possibly due to the stratospheric rpm). It’s still a solid motor.

I hope some of you find this project informative and can use the data I collect to help make decisions on your own project. If you have suggestions or comments on my test methods, post a reply so we can discuss. As mentioned earlier, if you have a particular component or modification that you would like to see included, let me know and we can collaborate.

Best regards, Mike

Title: Re: Evolution of a HotRod - Part 5 Camshaft
Post by Armen on 07/18/21 at 13:46:10

Awesome work as always!
Thanks!
Interested in seeing the pop top piston and the big bore pop top piston.