Yes, that's me. I do customs cams, and cylinder head work, primarily for Suzuki cars, but also for other things. I don't have any grinds suitable for the KLX.

My most popular performance build for one of the Suzuki's is to add about 24 degrees duration (at .050"), reface the head .040", then advance the cam 10 degrees. Stock intake centerline is 114. That's too late, so 10 degrees gives us 104, and refacing the head retards timing 2 degrees, and that leaves us with 106 degree intake centerline. Perfect for the application, with power from just off idle to about 7000 redline and a broad power curve.

 

I thought so, just forgot you actually did cam grinding. The cranium serves me well...

I remember some stuff about the Nighthawk S I had. It had really radical advance on the cams. Joe Minton degreed the cams in around 108 degrees and was happy with three horsepower, but the real gain was through the entire power range. I bought some sprockets, but never did the work, had to sell the bike due to layoff. I did do Marcelino's timing change though and disabled the KACR with better starting than ever.

Seems the magic advance numbers range between 100 and 110 degrees usually in the middle somewhere, as shown by your comments. I don't get it why the Japanese tend to do such large advance. I also kind of wonder why, if this sort of change works so well so often, it wouldn't work with the 351 or if there just isn't enough experience and results on it. Any thoughts?

We had a few guys wonder if this could be done on the KLX650 if the cams were that drastic on advance. No one has published any numbers yet. Maybe I check my valves soon and look.

It's always fun to pick the brain of someone with your kind of experience.

 

Glad to have you back Zomby... You bring perspective to the camshaft debate.

 

"Glad to have you back Zomby... You bring perspective to the camshaft debate."

+1

Never would have realized that longer duration with , perhaps, more overlap, would perfectly compliment advancing the overall timing. But it sure makes sense.

 

There are a number of reasons to phase the cams the way they do. Later timing is better for emissions (like in the Suzuki's I work on), and also makes for a more "friendly" power band, like wide lobe centers. It's one of those things that is really dependent on a number of other things, like overall duration, engine size, intake and exhaust efficiency, final drive gearing, and overall weight. For most high performance applications, 100-108 degree intake centerline seems to be what works best, but like duration and lobe centers, the larger the displacement, the higher you can go and still maintain the characteristics you're looking for. In other words, smaller displacement applications generally want less duration, more advanced IC, and tighter lobe centers because they don't have the displacement advantage to enhance torque.

 

thanks quys i didnt know what to do without you and the work of marcelino.

i solved the problems with the starter relay and clutch, i will soon post my impressions...

i dont know if the MCM would work with 351 kit but i know (from my little experience) that manufactures prefer more aggressive cams when increasing the displacement. aggressive camshafts means higher lift and more duration aka more overlap. With the MCM,the overlap is less than stock timing, so i believe that with the 351 kit the gain at low and midle rpm will be the same, but at high rpms probably there will be power loss.

i checked the valve pistons clearences. It seems that with the MCM for inlet i have 1,9mm and for exhaust 1,1mm. I think there is a slight contact for the exhaust valve also... I took the head out again i saw the contact, no problem with the valve (the contact was only during manualy rotating the crank, not with the engine start..)

i will keep the MCM for the inlet cam only. Can i estimate the hp gain only with the inlet cam MCM?

 

Kawasaki Forums - View Single Post - KLX 250 ( 300 ) camshaft mod by Marcelino

?

 

His numbers are wrong. Changing both cams, the same amount, at the same time has no effect on lobe separation.

That aside, even if it was 102, that's not necessarily too narrow.

 

"Changing both cams, the same amount (you)," in the same direction (me).

Reducing advance an equal amount on both cams means the cams are still timed the same relative to each other. The exhaust opens the same number of degrees rotation after the intake.

The timing change is relative only to the crank/piston position, right? Or am I missing something.

 

Yes, that is correct.

It looks like the mistake he made was in adding (degrees) instead of subtracting on the exhaust side, and that skewed the position, and resulting overlap.

It should not be referred to as increasing, or reducing advance, but as lobe centerline. Whether something is advanced or retarded is referenced only by it's original position.