Race Camshaft: Clarification? - Kawasaki ZX-10R.net
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post #1 of 24 Old 08-04-2007, 01:53 PM Thread Starter
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Race Camshaft: Clarification?

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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post #2 of 24 Old 08-04-2007, 03:18 PM
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Originally Posted by SalKhan View Post
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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post #3 of 24 Old 08-04-2007, 04:01 PM Thread Starter
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Wow that's both impressive (your effort) and incredibly lame-slash-confusing. Did you happen to call Kawasaki at all?

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post #4 of 24 Old 08-04-2007, 04:25 PM
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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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post #5 of 24 Old 08-04-2007, 06:37 PM
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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.


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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post #6 of 24 Old 08-04-2007, 07:06 PM
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Quote:
Originally Posted by JimmyJam View Post
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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post #7 of 24 Old 08-04-2007, 07:15 PM
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Quote:
Originally Posted by SecretAgent View Post
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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post #8 of 24 Old 08-04-2007, 07:51 PM
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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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post #9 of 24 Old 08-04-2007, 07:54 PM
 
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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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post #10 of 24 Old 08-04-2007, 08:06 PM
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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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