Cam lobe base circle varies in clearance.

Okay, I've been searching for a straight answer on this, and don't seem to find one. Has anyone run into this issue? My problem is that the cam lobe base circle is not perfect. Which I'm sure most kz's are not.

Where should I take my measurement from? TDC? cam lobe pointing directly away? or at the tightest point on the cam lobe?

I took a measurement at TDC and pointing directly away and got .10mm. When I rotate the cam a touch more it gets tighter than .05mm.

If I take my measurement from the tightest point on the cam base circle, what should I set the clearance for?

One person 3 years ago on this site said the lobes are not perfect and kawasaki told him years ago to point the cam directly away from the buckets and aim for the max clearance. Another person told me measure from the tightest point on the lobe and aim for the tightest clearance.

I want to get this right once and for all. I'm sick of taking the cams off :blink:

Thanks

I point them away,but everybody has their own way of doing things

Thanks wireman, but what I'm wanting to know is what should I set the clearance too with these tight spots being on the lobe. It seems the difference between pointing directly away and the tight spot is .05mm or more. So, if I set the clearance at .08 at pointing directly away, there is potentially a point on the lobe that is .03mm or smaller.

Thanks

Modern cams have opening and closing ramps. The cam designer wants to ease the valve open then gently close the valve. This greatly reduces the ware on the valve seats and extends the life of the springs, shims and cam lobes. The only reliable way to check and set the clearances is to point the lobe directly away from the bucket / shim.

You can set the intakes a couple shim sizes away from the tight side of scale since they tend to maintain clearance better than exhuast.
I set the exhuast closer to the middle since they get hot/expand a lot more than intakes do.

wireman wrote: I set the exhuast closer to the middle since they get hot/expand a lot more than intakes do.

What do you mean you set it closer to the middle?

Thanks

Middle of the scale for clearance on the shims to allow for expansion as things heat up

My thoughts have always been You want the valves closed at TDC compression stroke, "Duh " right?, so I've always measured my clearances at that point, and like wireman, I always shoot for the middle of the spec on the intake and a lil wider on the exhaust.

i have run into this as well. my thoughts are that if the clearance is toooo tight the valve wont close. so i use the tight spot, and shim to that.

mark1122 wrote: i have run into this as well. my thoughts are that if the clearance is toooo tight the valve wont close. so i use the tight spot, and shim to that.

Thanks guys,

Mark, what kind of clearance would you shim at the tight spot?

Set your clearance to recommended spec at the tightest point, so most guys would run .10-.15mm at that point.

RonKZ650 wrote: Set your clearance to recommended spec at the tightest point, so most guys would run .10-.15mm at that point.

X2