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Discussion Starter #1 (Edited)
O.K. I order a set of valve spring's for 04 ZX10r (Dominick) a very good friend of mine and was not impresed with the fit, so ordered another set from someone else and then another set and had 2 sets custom made in hope 1 of them were right.
Well after testing all the spring's that are being sold for the zx10 to the public the testing starts 1st at the seat pressure then .300 lift and .350 lift and .385lift spring pressure were you really need it at high RPM's
were the same as stock springs !!!
Well its a good thing I ordred some custom springs from Japan a couple of months ago because out of the 2 sets 1 is going to work perfect.

If anyone is going to add rpms to their bike you should have better springs
to stop valve float at high rpms.
If you are running stock cams you can order (NEW VALVE SPRING'S)
shim them 0.020" and rev an extra 350 rpm's safely
With the kawi intake cam and higher rpms you want to get different springs
GOOD LUCK FINDING ONES THAT WILL WORK!!
If you get in a bind and you need a set that work shoot me a p.m.

Set#1
Seat pressure 10 lbs over stock and 6.5 lb's at .385 lift
not bad could be a little higher at high lift,but dont like the fit of the stock valve cotter with their retainer that
comes with the spring, I am afraid it will wear the aluminum cotter down and drop a valve eventually.
Set#2 Seat pressure at 14 Lb's TOO HIGH at .385 lift 1 LB over stock
and some of the springs in this daul spring set up were very tigh and will cause friction untill worn in with miles, a good fit using all stock retainers.
Set#3 More seat pressure but less pressure at .385 lift than stock ???
Why the hell would I put a set of springs in anyones bike, when the spring
pressure is the same or lower at higher lifts, thats where the valve floats
when there is not enough spring pressure when it gets to the nose of the cam
at very high RPM's
Well the good news is the spring I have has 9 - 10 lbs at the seat and
10-12 lbs at .385 lift, this spring can also be set up for 10-12 seat and 14-16
at .385 lift.
Guys that know me know if it's not right its not going back together !
I hope this info comes in handy for some of you.
I dont like wasting money and seeing someone sell something that does not work the way it should.
 

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Thanks for the heads up.
 

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Were these stock valve springs?
 

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Discussion Starter #5
HKMP7 said:
Were these stock valve springs?
???????
Reread the above stock vs after market.
 

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was a little unclear
So none of these were kit springs from Kawasaki?
The aftermarket ones (who makes them)
 

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Discussion Starter #9 (Edited)
I am sending this back up top for the guy's building engine's on thier
zx10's and can't find a good valve spring.
I can help them out.
 

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good read ice man. I have a question for you. Im learning how to port and my teacher is telling me im doing too good of a job. that being said i made the walls of my test head Smooth i mean babbys ass smooth. he told me it needed to feel like a cats toung to keep the ai turbulent and the AF mixture up...well ok but should i go Smooth if i go the turbo rought? then the air pressue should keep the af mixture with motion. Confused...?
 

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Interesting stuff Iceman, sometimes a manufacturer will put a stronger spring in initially to stop bounce, this is pretty normal stuff to stop us over zealous wannabe GP stars from damaging our engines when we constantly hit or go through the mandated "redlines".
I have had instancies where softer springs have been just fine and have eased up the load in the valvetrain considerably but I wouldnt recommend it for the average street rider , the optimum spring is the one weakest enough to do the job , however this can only be done by trial and error and is quite a costly exercise.

Way back , when the world was still black and white I worked in development on quite a few twin cam engines , we ran load cells on timing chains and cambelts in a variety of places to analyze such anomolies to see if we could optimize the valve gear for racing purposes , I remember an instance where we gained another 700 RPM on a 7500 RPM motor , of course the only way to prove this was to take the engine past its point of self destruct , that was a part of my job I really enjoyed !!



If in doubt....OEM.
 

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hey thanks guys! i dont like the answers but hey i love the advice. thanks again
 

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Hey 10 , you can polish the hell out of the exhaust ports , but the intakes need a rough finish to create turbulence and reduce the boundary layers created on the outsides of the ports ,basically giving you a freer flowing port with lots of turbulent air/fuel mixture pre valve.
 
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