Valve Clearance Changes With Cam Position

Also, check the torque for the cams before ordering shims. I have had it happen where the measurements change after torquing the cams to the correct spec.
Good luck.

racer54 wrote:

I have run into a few instances where the top face of the shim cup was worn into a "cup" on the face. Measure it one time and the clearance would be .004 turn the motor over, the shim cup turns and the "cupping" moved also and the clearance would measure .009 for example. Took a while before I figured it out but it's one of the things I check for now if clearances look funny in any way. Something to think about. Motor gets hot and the cups lose some of the heat treat, I was told, and they start to wear over time.

Really good point.

Many thanks to all who replied. We are in the process of moving and I have not had time to work on the bike yet.
RonKZ650 - I will try turning the cam through its entire base circle while checking with feeler gauges. Will see what the variation in readings is.
newbikekiller - After cleaning the pilot jets I held each one up to the sky to be sure that the amount of light I could see was consistantly bright. Pretty clean I would hope.
jcote75 - I will check my intake boots. Good idea.
tjettim - My understanding of the quieting ramps is a small section of the cam, just before the lobe, where the clearance is gradually reduced to smooth out the slack in the valve train, so that the lifter is not popped against the bucket so hard. Reduces tapping noise.
larrycavan - I will check compression. I would think the magic marker would only get rubbed off on the lobe of the cam and not the back side, unless clearance is less than zero.
Bluemeanie - I would think that a cam grinder would hold tolerance of less than .001" variation on the base circle of the cam, so that it would not matter where the clearance is measured, as long as you stay well away from the lobe.
Racer54 - The worn or distorted bucket idea certainly has merit. I plan on checking clearance as I rotate the bucket on intake #4, to see what variation I get in readings. I am not so sure that the bucket may have gotten a little tight at some point of rotation. This would surely explain my sub-standard performance at low RPMs. My belief is that if the #4 intake is not seating 100%, that the compression may blast back past the intake valve, partially filling the intake port, and diluting the incoming mixture to the point that it misfires. At higher RPMs the incoming volume and velocity is great enough that the valve leakage is not significant. I just hope the valve is not somewhat burned.
cafekz750 - All cam caps were good and tight.

Thanks again to all for their input. I will let you know what I discover when I find time to work on the bike.

Bill Baker
1982 KZ650 CSR
Houston, TX

since the goal is to have the valves seated.i would think u should set the clearance to the smallest clearance.aftermarket cams recomend higher clearance specs(.006" on WEB's),so there should be no real down sid to running to the upper kawi spec to satisfiy a tite spot.i just bought brand new Web cams and installed then yesterday and found them to have .002" dif clearance on the same lobe ,on a couple lobes.Hope this helps.good luck.

I have noticed over the years with stock
and several cam grinds a small amount of
variation in the base circle to shim
clearances.On the average,the bottom of
the lobe,directly opposite from the highest
point gives the most consistent measurements.
I would rotate the motor and double check when
in doubt,exspecialy with underbucket shims.
After having the same bike now for 30 years,
the way I adjust the valves just seems routine now.