Shimming when there's no clearance

Five of my valves have no clearance at all between the cam lobes and the other three are at about .7mm, which is a little under spec.

Is there a way to figure out what size shims I'm going to need? Maybe take the shim out altogether, measure the clearance and subtract the amount of clearance I need? Any other ideas?

Thanks!

do the buckets turn in the bores or are they too tight for that even

look at all your shims, and find the smallest, use it as a base line for the rest assuming you can get some clearance from the small shim

BSKZ650 wrote:

look at all your shims, and find the smallest, use it as a base line for the rest assuming you can get some clearance from the small shim

makes sense to me

chrispysaki wrote:

Five of my valves have no clearance at all between the cam lobes and the other three are at about .7mm, which is a little under spec.

Is there a way to figure out what size shims I'm going to need? Maybe take the shim out altogether, measure the clearance and subtract the amount of clearance I need? Any other ideas?

Thanks!

If smallest feeler gauge won't fit between shim and cam base circle, but shim itself can be moved --- indicates existence of some minimal clearance. Could remove shim, determine its size, and replace with next thinner size.

If smallest feeler gauge won't fit between shim and cam base circle, but shim itself cannot be moved --- indicates no clearance whatever. Could remove shim, determine its size, and replace with shim two sizes thinner.

In any event, after measuring clearance, must know size of existing shim in order to determine needed replacement size.

With clearances properly adjusted to specs, it's a good idea to make note of each valve's shim size to keep with bike maintenance record. Then in future, will know replacement shim size needed from gap measurement alone.

Good Fortune!

if the buckets will turn then i would go 3 sizes smaller on the exhaust and 2 sizes smaller on the intakes and that should get your right in spec or a little bit looser than spec. which is way better than tight.

Thanks, all. I didn't check if the buckets will turn before removing the cams. I'll check that out and see if using the smallest shim creates any clearance and go from there.

what bike are you working on, since you removed the cams guessing its a under bucket shim

Specified valve clearances for Z1~KZ900~KZ1000 with over-bucket shims are .05mm~.10mm, with shim sizes available in increments of .05mm.
Up to .15mm clearance is reportedly okay. But I would suspect loses some flow, however minimal.

Other KZ models, with under-bucket or over-bucket shims, have specified valve clearances which differ among the various models.

In this application, looser is better than tighter. "When they're click'n, they ain't stick'n."

Good Fortune!

It's an '80 kz750-4. Underbucket shims. Spec clearances are .08 to .18.

In my original post I reported .7mm, but that should have been .07.

that is why i use standard measurements instead of metric. no confusion that way. i try for .004"=.10mm intake .006" =.15mm exhaust. besides my feeler gauges read in standard.

I hope this isn't highjacking, but I'm doing some of the same work, on my 78' 650 and just waiting for a day to pull the cams and find out just what size shims I have in there.

I'm getting some chatter, and none are over 0.010", so all very close to spec clearance. However, a few get no clearance on my smallest feeler gauge, which is 0.08" (spec). So while its hard to say what the actual clearance is, none of the buckets are completely immobile.

Reading through this string, I wonder if anyone has any tried and true advice on adjusting the clearances in this model/engine? I figure I'll just shoot for manual specs. But I gather generally a little looser, especially on the exhaust side is gonna be a.o.k? I understand the principles at work here, and am not attempting to sqeeze every ounce of possible performance out of the engine, rather have it run reliably and last a good long time. (which it does currently, and should continue to do

Thanks,

Jon