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Message started by DragBikeMike on 08/02/21 at 01:05:07

Title: Evolution of a HotRod - Part 7 - Cylinder Head
Post by DragBikeMike on 08/02/21 at 01:05:07

This is the seventh 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 (home-built). 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. The larger carb and filter extended the upper rpm limit. Overall performance was improved. You can find Part 4 here.

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

Part 5 installed a new camshaft with higher lift and duration. The results were gratifying and informative. Big power gains were evident. Now, with some valve overlap, the exhaust header took on a new role. You can find Part 5 here.

http://suzukisavage.com/cgi-bin/YaBB.pl?num=1626391255

Part 6 installed a lighter flywheel. The results were surprising. Acceleration in the lower gears was improved, while top speed suffered a bit. You can find Part 6 here.

http://suzukisavage.com/cgi-bin/YaBB.pl?num=1626921647

Part 7 installs a ported cylinder head. The Stage II head flows significantly better than the stock head. More airflow equals more power. It’s an eye opener.

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 7 - Cylinder Head
Post by DragBikeMike on 08/02/21 at 01:06:45

Up to this point, we have managed to improve acceleration and top speed by increasing air flow through the engine. A Free-flowing air filter and exhaust were simple additions that worked great. A larger carb extended maximum rpm and improved throttle response. A camshaft with more lift and duration improved cylinder filling and took advantage of the inertia in the column of air. The light flywheel (the only modification not intended to increase air flow) was underwhelming. A little faster in the lower gears but a little slower in top gear.

Why argue with success? Give it more air.

A ported cylinder head is easy to do and, if done correctly, will provide significantly more airflow. You can pull off a port job for the cost of a new set of valve seals, a head gasket, and a few hours of elbow grease.

For a 40 cubic inch engine, the LS650 has very small valves. The intake valves are only 33mm, and the exhaust valves are only 28mm. A typical high-performance 650 has 38mm intakes and 33mm exhausts. But even with the small valves, you can still achieve dramatic improvements in air flow.

Title: Re: Evolution of a HotRod - Part 7 - Cylinder Head
Post by DragBikeMike on 08/02/21 at 01:12:00

About three years ago, Fast650 turned me on to an article about a home-built flow bench. It was a simple device. I decided to build one using the concepts discussed in the article. Mine isn’t nearly as nice, but it’s perfect for our LS650 cylinder heads. The bench is not calibrated, but it will verify an improvement in flow, and it quantifies the improvement as a percentage. It’s a tool that can measure flow and provide consistent, repeatable data.

Once I had a tool to measure flow, I started experimenting with various port modifications. The Stage II and Stage III heads were developed using the little flow bench. We will be installing a Stage II head. I have a well-used specimen. It’s perfect for this project.

The head has a set of DR650 valves (33mm/28mm), RD valve spring kit, and shortened valve guides (all to accommodate the additional lift of a Web 340b cam). The DR valves, RD spring kit, and shortened valve guides have absolutely no affect on flow, they simply accommodate the higher lift cam.

The Stage II modifications include:

-Raised intake port floor

-Widened intake port runners

-Exhaust port outlet enlarged to 1.5”

-Exhaust port guide bosses radiused

-Blended valve seats and bowls

-Back-cut valves

In this post, I’m not going into all the details of the port modifications. If you review these old posts, you will see that the stuff I summarized above is very easy to accomplish. You don’t need to change the valves, valve springs, or retainers. The stock components work fine with the DR650 cam. The old posts provide port maps, dimensions, required materials, and most of the how-to. The Stage II head is essentially the same as the Stage III except for the 34mm intake valves and the 1.79” exhaust port outlet.

http://suzukisavage.com/cgi-bin/YaBB.pl?num=1554362214

http://suzukisavage.com/cgi-bin/YaBB.pl?num=1595224521/0

Title: Re: Evolution of a HotRod - Part 7 - Cylinder Head
Post by DragBikeMike on 08/02/21 at 01:13:32

Remember, my home-made bench is not calibrated, so the actual flow values may not be accurate in terms of cubic feet per minute (CFM), but the percentage of change should be spot on. That means the graphs accurately depict the change in flow.

This graph shows the intake flow of a stock head compared to a Stage II ported head and a Stage III ported head. At max flow, the Stage II has a 17% advantage over the stock intake port.

Title: Re: Evolution of a HotRod - Part 7 - Cylinder Head
Post by DragBikeMike on 08/02/21 at 01:14:28

This graph shows the exhaust flow of a stock head compared to a Stage II ported head and a Stage III ported head. At max flow, the Stage II has a 19% advantage over the stock exhaust port.

I think the Stage III exhaust port should be reserved for larger displacement applications (97mm bore) with the larger Mac header (1.79”). The Stage II port (1.5”) works good on smaller displacement applications (94mm bore) with the stock header.

Title: Re: Evolution of a HotRod - Part 7 - Cylinder Head
Post by DragBikeMike on 08/02/21 at 01:15:32

You can see from the graphs that the Stage II head outperforms the stock head on the flow bench. Question is, will it make a difference on the road? Let’s find out.

These pictures show the head I used for this part of the project. It has about 8000 miles on it. I installed it as-is, didn’t even disassemble for inspection. Just cleaned up the sealing surfaces and slapped it on.

Title: Re: Evolution of a HotRod - Part 7 - Cylinder Head
Post by DragBikeMike on 08/02/21 at 01:16:20

I use epoxy to raise the intake port. You can see from this picture that the epoxy is stained, but it’s still in good condition. It’s hangin in there. The intake port doesn’t get very hot. The intake valves are a little crusty, but it wasn’t worth the trouble to disassemble and clean. Ain’t gonna win no beauty contests, but she’s solid.

Title: Re: Evolution of a HotRod - Part 7 - Cylinder Head
Post by DragBikeMike on 08/02/21 at 01:17:02

The exhaust port is an ugly beast. The factory made what appears to be a lousy port. But looks are deceiving. Opening up the circular outlet from 1.3” to 1.5” does wonders (Just look at the flow graph). You can really amp up this port, but I suggest you stick to 1.5”.

Title: Re: Evolution of a HotRod - Part 7 - Cylinder Head
Post by DragBikeMike on 08/02/21 at 01:18:02

Another part of the exhaust port that responds well to grinding is the left runner. It has a straight vertical wall that can be rounded out with a carbide burr. The yellow line shows where to grind. Don’t get carried away, just make it round and blend it in. My old post regarding the Stage III head provides good details.

Title: Re: Evolution of a HotRod - Part 7 - Cylinder Head
Post by DragBikeMike on 08/02/21 at 01:19:05

The left runner should look like this.

Title: Re: Evolution of a HotRod - Part 7 - Cylinder Head
Post by DragBikeMike on 08/02/21 at 01:20:24

The intake valve stems looked OK, round wear patterns centralized in each stem. The retainers & cotters looked good too. As mentioned previously, the stock valves, retainers, cotters and springs work perfectly with the DR650 cam, the RD spring kit is not necessary. I didn’t want to change these parts. They shouldn’t have any effect on the acceleration tests and I didn’t want to tamper with the head.

Title: Re: Evolution of a HotRod - Part 7 - Cylinder Head
Post by DragBikeMike on 08/02/21 at 01:21:21

The tips of the exhaust valves had a problem. One valve is obviously not rotating, and the other appears to have questionable rotation. Of course, I would prefer that they rotate, but I have no idea why they aren’t rotating, or what I could do to make them rotate. There wasn’t any evident damage, so I left it the way I found it.

Title: Re: Evolution of a HotRod - Part 7 - Cylinder Head
Post by DragBikeMike on 08/02/21 at 01:21:59

Back in April, during a routine inspection I found a chunk missing from an adjuster. It was on the intake rocker arm. I attributed the fracture to edge loading. The 340b cam has a lot more lift. The extra lift appeared to swing the adjuster screw far enough to cause the sharp edge of the screw to contact the valve tip.

Title: Re: Evolution of a HotRod - Part 7 - Cylinder Head
Post by DragBikeMike on 08/02/21 at 01:22:36

I scrounged up a replacement screw and used a Dremel tool to reduce the radius of the tip.

Title: Re: Evolution of a HotRod - Part 7 - Cylinder Head
Post by DragBikeMike on 08/02/21 at 01:23:32

Then polished it up. It came out good, so I did the same thing to the other three screws.

Title: Re: Evolution of a HotRod - Part 7 - Cylinder Head
Post by DragBikeMike on 08/02/21 at 01:24:22

The polished stock screws were holding up, but I wanted a better fix. I found these adjusters on-line, so I figured I would give them a try. They are from a 1983 through 2004 Husqvarna 510, 570, 610 or 630. Those bikes redline around 7K to 8.5K so they looked like a good choice. They have a tighter radius and a bigger contact pad. Cagiva part number 16-15-049-01.

Title: Re: Evolution of a HotRod - Part 7 - Cylinder Head
Post by DragBikeMike on 08/02/21 at 01:25:02

Only downside seems to be removal and replacement. The stock screws can be replaced without removing the head cover. These Cagiva screws require removal of the head cover. They fit the rocker arms perfectly.

Title: Re: Evolution of a HotRod - Part 7 - Cylinder Head
Post by DragBikeMike on 08/02/21 at 01:25:50

A change like this requires that the adjuster contact be checked to make sure it doesn’t get too close to the edge of the valve tip. Mark the valve tips with a sharpie marker pen, then assemble the engine (no sealant) and rotate the crankshaft through several turns.

Also, the intake adjuster tips sit high, so I did a clay check. Wouldn’t want the adjusters hitting the valve cover.

Title: Re: Evolution of a HotRod - Part 7 - Cylinder Head
Post by DragBikeMike on 08/02/21 at 01:26:34

Tip contact was centralized on all four valves. Should be OK.

Title: Re: Evolution of a HotRod - Part 7 - Cylinder Head
Post by DragBikeMike on 08/02/21 at 01:27:14

The clay check showed plenty of clearance. No problems here. The way I see it, the Cagiva adjusters are either gonna work great or wreck the engine. No guts no glory, chance-um.

Title: Re: Evolution of a HotRod - Part 7 - Cylinder Head
Post by DragBikeMike on 08/02/21 at 01:28:25

This Stage II head incorporates a jack bolt to buck-up the rear chain guide and restore tensioner plunger engagement. When I started the head swap, the plunger was at 16.5mm. During reassembly, I adjusted the jack bolt to reposition the plunger to 12mm. With the jack bolt feature, periodic adjustments are possible. Now when I remove the clutch cover, I can inspect the tensioner and set it back to 12mm. It’s a nice feature.

The jack bolt is just a piece of continuously threaded 5/16” rod. The cylinder head must be spot-faced, and then drilled & tapped. Of course, you do that when the head is off the engine

Title: Re: Evolution of a HotRod - Part 7 - Cylinder Head
Post by DragBikeMike on 08/02/21 at 01:29:25

It’s nice to be able to restore the plunger engagement rather than change guides, tensioner, or chain.

Title: Re: Evolution of a HotRod - Part 7 - Cylinder Head
Post by DragBikeMike on 08/02/21 at 01:30:12

Once adjusted to the desired position, the jack bolt is locked in place with this special cap.

Title: Re: Evolution of a HotRod - Part 7 - Cylinder Head
Post by DragBikeMike on 08/02/21 at 01:30:56

Things could get ugly if the jack bolt came loose, it’s wise to safety wire the cap.

Title: Re: Evolution of a HotRod - Part 7 - Cylinder Head
Post by DragBikeMike on 08/02/21 at 01:35:46

Removal and replacement of the cylinder head is straightforward. It’s like doing a cam swap (plus a few more steps). Part 5 of this series has good info on cam replacement. While the head is off, modify the ports as discussed in the links I provided. If you have an extra head, you can do the port work, then install it when convenient.

Set valve clearance to .005” and fill the crankcase with oil. I must confess that I switched oil. It was getting a bit too expensive. I’m into this thing every week or two and I usually don’t re-use oil. The Rotella T4 costs half of what Castrol V-Twin oil costs, and probably only one-fourth of what Mobile 1 V-Twin oil costs. The Rotella will do for now.

A quick compression test pumped 160 psi. No change. Makes sense. Same cam. Same 56cc combustion chamber. Same piston….. Didn’t really do anything that would affect the compression ratio. Ready for test.

How does it run? Just fine. Starts right up, idles smooth, revs quick. It will absolutely bury the 8K tach. No oil leaks. No unusual noise. The Cagiva valve adjusters survived a few laps around the block. It’s always encouraging when your trick parts don’t fail in the first five-minutes of operation.

It was time for WOT acceleration tests.

Let’s review the setup. Stage II ported head, DR 650 cam, 3” flywheel, 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. Except for the ported head, everything is the same as it was for the Part 6 flywheel test.

I left the jetting as-is, a #35 pilot jet, #145 main jet, and the needle clip in the fourth groove (rich).

Second Gear 4K to 7K: 2.73 seconds 0.19 seconds faster than stock head

Third Gear 4K to 6.5K: 4.87 seconds 0.26 seconds faster than stock head

Third Gear 4K to 7K: 6.95 seconds 0.58 seconds faster than stock head

Fifth Gear 3.5K to 5K: 4.58 seconds 0.46 seconds faster than stock head

Fifth Gear 3.5K to 5.5K: 6.96 seconds 1.00 seconds faster than stock head

Wow! That’s one sweet modification. Nice fat improvements across the board. Fifth gear pull to 5500 rpm is killer. In addition, maximum rpm in third gear has increased by 100 (7550 vs 7450) and maximum rpm in fifth gear has increased by 400 (6450 vs 6050). The porting doesn’t hurt the low end at all, and it extends the top end a bunch.

What will happen when we throw on the Mac header?

Title: Re: Evolution of a HotRod - Part 7 - Cylinder Head
Post by DragBikeMike on 08/02/21 at 01:38:40

A quick header swap and it was time to take it for a spin. The air/fuel ratio was good, so I left the jetting right where it was. It tends to go a bit rich at very high rpm. That seemed like a safe place to be.

Second Gear 4K to 7K: 2.68 seconds 0.05 seconds faster than stock header (a wash)

Third Gear 4K to 6.5K: 4.82 seconds 0.05 seconds faster than stock header (a wash)

Third Gear 4K to 7K: 6.60 seconds 0.35 seconds faster than stock header

Fifth Gear 3.5K to 5K: 4.76 seconds 0.18 seconds slower than stock header

Fifth Gear 3.5K to 5.5K: 7.19 seconds 0.23 seconds slower than stock header

It’s difficult to tell the difference until it starts running up around 6500 rpm, then it becomes evident that the Big Mac loves the stratospheric rpm. The Big Mac pulls an additional 200 rpm in third gear (7750, that’s 90 mph), but still signs off at 6450 in fifth gear. That wall of air is tough to penetrate. It drives right through the high-speed stall we experienced at 6050 rpm with the stock head and light flywheel.

Selecting a pipe for this head is easy, they both run great.

Title: Re: Evolution of a HotRod - Part 7 - Cylinder Head
Post by DragBikeMike on 08/02/21 at 01:41:51

Oil temperature and cylinder head temperature remain about the same (210/310), as does oil pressure. Fuel economy is also about the same (55.4 mpg). There’s no discernible change in audible noise. Tha Cagiva adjuster screws are quiet (always a good sign).

This completes the cylinder head portion of the project. The Stage II ported head was a huge success. Performance has improved everywhere. The biggest improvement was fifth gear acceleration (IMO, the most important test, passing power).

It is a relatively easy and inexpensive modification that will provide significant measurable improvements in performance, regardless of the cam or the compression ratio. It demands free-flowing induction and exhaust systems. It ain’t gonna work if you choke it off.

At this point, I have done 180 WOT acceleration pulls to dial in the different combinations. There’s a little over 2600 miles on the engine since we started the project. 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. It’s still a solid motor.

Next stop on the Power Train? Compression. Let’s see what happens when we bump up the squeeze. Part 8 will install a Wiseco piston.

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 7 - Cylinder Head
Post by Ruttly on 08/02/21 at 10:11:57

DBM, Why was epoxy used in the intake ? Was there a low spot there ? Maybe area where fuel was pooling ? My intake side only needed in my opinion some minor shaping ,mostly in valve pockets. In comparison to that horrible exhaust side that took some work to get it to flow. Keep in mind that I wasn’t trying to build a high H/P , just one that breathes well.

Title: Re: Evolution of a HotRod - Part 7 - Cylinder Head
Post by DragBikeMike on 08/02/21 at 11:27:44

I'm glad you asked that question Ruttly. I consider the epoxy buildup the most beneficial feature of the Stage II head. Raising the floor of the intake port allows you to increase the short-side radius. The column of air tends to lift off the bottom of the port as it makes the tight turn just before the valve seat. That causes the air to pile up on the top side of the port. You can see from this sketch that the short side radius is much larger (red line).

Title: Re: Evolution of a HotRod - Part 7 - Cylinder Head
Post by DragBikeMike on 08/02/21 at 12:01:29

As I was playing around on the flow bench, I noticed that when I inserted a large screw driver into the port and moved it around, flow would increase when the screw driver was positioned on the bottom of the port, just before the turn.

I got to talking with Fast650 about that and he turned me on to some posts on a Kawasaki forum. The desert racers were using epoxy to improve that lower radius. Then I found supporting info in your favorite book, Four-Stroke Performance Tuning. Take a look at page 80 of Bell's masterpiece.

Using modeling clay, I was able to achieve dramatic increases in flow when I built up and reshaped the floor of the port. Almost all of that 17% flow improvement comes from the epoxy build-up. Cleaning up dingleberries and blending the seats barely moves the needle. The BIG improvement comes with the epoxy build-up and widening the port. It's important to get the shape correct. As long as the apex of the radius is positioned as shown in the sketch, it works good. Without that little flow bench, I would never have seen this treasure chest.

Typically, the pros build up the floor by welding, and raise the roof of the port so as not to reduce the cross section. I feel the roof of the LS port is too thin to permit grinding away a lot of material, so I build up the floor and widen to compensate.

The flow bench numbers show that it improves flow. Performance on the road proves it. 8-)

Title: Re: Evolution of a HotRod - Part 7 - Cylinder Head
Post by Armen on 08/03/21 at 03:38:54

As always, excellent and informative.
With one bike running, and about 7 not, the Suzi-Q is prob about third on the Wake Up que.
Part of the evil of moving is finding all the stuff that got 'put somewhere'. I know I have another head somewhere. I'll start looking soon....
Keep up the good work!
thanks again