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Was just going through the Kawasaki Race Parts catalog and I noticed that the Intake Race Cam Shaft states it should be used with stock springs and stock exhaust camshaft, but the exhaust camshaft needs new springs and says nothing about the intake camshaft.

Any idea what the method to the madness is?
 

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Was just going through the Kawasaki Race Parts catalog and I noticed that the Intake Race Cam Shaft states it should be used with stock springs and stock exhaust camshaft, but the exhaust camshaft needs new springs and says nothing about the intake camshaft.

Any idea what the method to the madness is?

I will take a shot at this since I bought and measured all this stuff.


There are 4 different cams and 3 different springs.

Stock intake cam 9.2MM lift

Race intake cam 9.7MM lift

Stock Exhaust Cam 8.5MM lift

Race Exhaust cam 8.0MM lift

Stock intake springs 122lbs pressure

Stock exhaust springs 85lbs pressure

Race springs 127 lbs pressure.

What Kawasaki did to extract ever bit of power from the stock motor was to use lightweight Titanium exhaust valves and weak exhaust springs that work OK with lite weight valves to stop power robbing from the crank. Springs sap power from the crank. These are the weakest stock exhaust springs I have ever measured.

Funny thing is, the RACE exhaust cam has less lift so why the recommendation for stronger springs? That is the real mystery. I have emailed Attack Performance and Kawasaki HQ’s and have got no replies. No one knows the answer to this for a fact. I suspect Kawasaki just screwed the pooch.

Why a RACE cam with less lift on the exhaust? Makes no sense. I understand that this is all parts of an overall race kit package, but still makes no sense that there would be piston to valve clearance problems if you were using the race pistons. There should be plenty of relief in the valve pockets.

There is not much difference on the spring curve between the stock intake and race springs. So I would think the race intake with stock springs would be OK as long as you weren’t using a Dynojet Ignition module to increase redline. Then you might want the race springs on the intake side.

Most people who have tried the race exhaust cam lose power. No reason to wonder why. Less lift and stronger power robbing race springs.

Makes no sense.

Buy the RACE intake cam, throw it in, degree both it and the stock exhaust cam and forget the rest.

JJ
 

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my theory on the exhaust cam is this....although the lift is smaller the lobe seperation is changed thereby changing overlap and raising the torque curve to the higher rpm range. a smaller cam therefore also puts less of a load on the exhaust valve springs so, when combined with the raised redline that the cam is designed for, the stock springs don't have the pressure to return positively and therefore create a minimal amount of valve float.

anyways, that's just my theory. i've encountered such problems building SBC motors, i don't see why the physics would be different in a motorcycle engine.
 

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my theory on the exhaust cam is this....although the lift is smaller the lobe seperation is changed thereby changing overlap and raising the torque curve to the higher rpm range. a smaller cam therefore also puts less of a load on the exhaust valve springs so, when combined with the raised redline that the cam is designed for, the stock springs don't have the pressure to return positively and therefore create a minimal amount of valve float.

anyways, that's just my theory. i've encountered such problems building SBC motors, i don't see why the physics would be different in a motorcycle engine.
:+1:

You raise the redline thats the reasons for heavier springs I got with the kit parts 13,826 rpm stock revs to 12,600 I believe not sure tho.
 

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I will take a shot at this since I bought and measured all this stuff.


There are 4 different cams and 3 different springs.

Stock intake cam 9.2MM lift

Race intake cam 9.7MM lift

Stock Exhaust Cam 8.5MM lift

Race Exhaust cam 8.0MM lift

Stock intake springs 122lbs pressure

Stock exhaust springs 85lbs pressure

Race springs 127 lbs pressure.

What Kawasaki did to extract ever bit of power from the stock motor was to use lightweight Titanium exhaust valves and weak exhaust springs that work OK with lite weight valves to stop power robbing from the crank. Springs sap power from the crank. These are the weakest stock exhaust springs I have ever measured.

Funny thing is, the RACE exhaust cam has less lift so why the recommendation for stronger springs? That is the real mystery. I have emailed Attack Performance and Kawasaki HQ’s and have got no replies. No one knows the answer to this for a fact. I suspect Kawasaki just screwed the pooch.

Why a RACE cam with less lift on the exhaust? Makes no sense. I understand that this is all parts of an overall race kit package, but still makes no sense that there would be piston to valve clearance problems if you were using the race pistons. There should be plenty of relief in the valve pockets.

There is not much difference on the spring curve between the stock intake and race springs. So I would think the race intake with stock springs would be OK as long as you weren’t using a Dynojet Ignition module to increase redline. Then you might want the race springs on the intake side.

Most people who have tried the race exhaust cam lose power. No reason to wonder why. Less lift and stronger power robbing race springs.

Makes no sense.

Buy the RACE intake cam, throw it in, degree both it and the stock exhaust cam and forget the rest.

JJ
Nice. Now include the durations
 

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my theory on the exhaust cam is this....although the lift is smaller the lobe seperation is changed thereby changing overlap and raising the torque curve to the higher rpm range. a smaller cam therefore also puts less of a load on the exhaust valve springs so, when combined with the raised redline that the cam is designed for, the stock springs don't have the pressure to return positively and therefore create a minimal amount of valve float.

anyways, that's just my theory. i've encountered such problems building SBC motors, i don't see why the physics would be different in a motorcycle engine.
Sounds about right to me.
 

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I believe when used all together as a kit it maybe a power adder. I was thinking since they use 14.3:1 pistons the taller pistons might need more clearance.

Ive been running stock exhaust and race intake for a long time, I Was going to try mega cycles but they are so damn expensive and you need to find good springs as well.
 

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Wow that's both impressive (your effort) and incredibly lame-slash-confusing. Did you happen to call Kawasaki at all?
Perhaps you didn't read where he typed that he tried to contact both Attack and Kawasaki for the answers?
 

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I've asked around about the kit ex cam, Doug Meyer (formerly of Muzzys) didn't know, is asking around, but it is definitely unusual.

Here's the specs with total duration.

 

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Nice. Now include the durations
I didn't include the durations because I felt it wasn't material to the discussion about the need for stronger valve springs with a cam that has less lift.

Duration #s are like dyno #s, its how you measure them. If you start measuring when the valve starts to open to the valve is fully closed you get some big duration #s. I have always measured at 1MM of lift. In other words I set my dial indicator on the valve and open it .040", take a reading, close the valve till its .040" from being closed and that is the duration. Some engine builders use .050". So, only you can compare 2 cams back to back using the same lift figures. If you dont know what lift figure is used, then you realy have no clue as to what #s someone gives you.

The reason I use 1MM of lift is that there is so much duration on the opening and closing ramps of the cam that it exaggerates the #s. Most engine builders agree that valves open less than .040 inch are not flowing any significant amount of air, so those numbers below .040" lift are meaningless.

JJ
 

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I've asked around about the kit ex cam, Doug Meyer (formerly of Muzzys) didn't know, is asking around, but it is definitely unusual.

Here's the specs with total duration.

I agree it is definitely unusal, and no one seems to know. The duration #s you posted are meaningless to compare against other cams, when you don't know what lift they are measured at as I have described above.

JJ
 

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Very true words, some manufacturers give you the duration from the tangential point of the cam to the base circle and others from 0.040" of lift when the cam starts to be effective.
 

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Right on. Had to ask. I also used the .05 in the past. Curious as to the future. Thanks
 

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Discussion Starter #15
Perhaps you didn't read where he typed that he tried to contact both Attack and Kawasaki for the answers?
Geezus...

Must be Aphasia kicking in. I do remember him writing it and then totally forgot 3 seconds after reading it. HA! My mistake!

I'm surprised Attack hasn't called back if anything... they're usually pretty good about getting back - at least for littler things?
 

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Geezus...

Must be Aphasia kicking in. I do remember him writing it and then totally forgot 3 seconds after reading it. HA! My mistake!

I'm surprised Attack hasn't called back if anything... they're usually pretty good about getting back - at least for littler things?
You know you are in a forum and not the laundromat , right ?..lol.
 

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a guy down south in FL bought an attack racing zx10r and with their motor which is all kawi bolt ons made i think 187hp..... not bad for stock bore.
 

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Geezus...

Must be Aphasia kicking in. I do remember him writing it and then totally forgot 3 seconds after reading it. HA! My mistake!

I'm surprised Attack hasn't called back if anything... they're usually pretty good about getting back - at least for littler things?
I have sent numerous emails to Attack, and they have been great to answer all of them, except this one. I even forwarded it to them twice, and nothing.

JJ
 

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I agree it is definitely unusal, and no one seems to know. The duration #s you posted are meaningless to compare against other cams, when you don't know what lift they are measured at as I have described above.

JJ

Of course. Comparisons should always be made using the same measuring procedure, and with zero lash.

I posted the OEM duration values to show the difference between the stock and kit exhaust cam. Using the same procedure, the kit cam has 10 degrees less total duration. However, we know nothing about lobe shape, which could moderate the difference. But I doubt it.
 

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Ive used the race ex cam with the harder springs, it is still climbing in pwr to the rev limter so it could use the kit ecu or ignition module to increase the limit for sure.
 
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