Valve clearance: not enough? or too much?

The clearance on my intake valves is within spec, but my exhaust valves had no measurable clearance with my smallest feeler guage (.038mm)

This is a '79 KZ750 twin with those large, hard to find, 32mm valve shims on top of the bucket. Clearance spec according to my manual is .05-.1mm.

The shims that were installed were 250s. The only smaller shims I can find are 235s (from Z1). That results in .152mm of clearance on my left cylinder and .229mm on the right.

So until I find proper shims, which is better: to run with no valve clearance or to run with too much?

Too little lash can lead to burned valves = bad.

However, I am a bit confused by the math here, or maybe I just don't understand the whole thing.

Let's say the lash is actually .035. The difference between a 250 shim and a 235 shim is .015, isn't it? If we add .015 and .035, we get .050, not .152 or certainly not .229. If the lash is zero or less, the final lash with the 235 shim will be .015 or less.

Or maybe I'm just a mo-ron :silly:

Wait, you're right. I need to go check my clearance again.

2.35(shim) + .229(clearance) = 2.579

So with the 250 I should have .079 which would be within spec.

Time to get the feeler gauges out again and double check.

I think one of my 250 shims isn't really a 250. Its stamp had been worn off and I don't have a micrometer so I took it to the local shop (who told me over the phone they had some 32mm shims, but didn't) and they measured it there.

They told me its a 250, but now I think its more like a slightly worn 260.

I swapped some shims around and now all but one is within spec. It's the exhaust valve on the left cylinder.

It has a 235 in it (at least so the stamp says) and .15mm clearance (spec is .05-.1). I have another 250 which takes the clearance down to 0. Finally something makes sense.

I need a 240 but can't seem to find one. So my original question still stands, though with slightly different details.

Which would be better, a valve with no clearance or a valve with a little too much?

Maybe I should say which would be less bad?

Topper wrote:

...swapped some shims around and now all but one is within spec. It's the exhaust valve on the left cylinder.
It has .15mm clearance (spec is .05-.1). I have another 250 which takes the clearance down to 0... eed a 240 but can't seem to find one. So my original question still stands, though with slightly different details.
Which would be better, a valve with no clearance or a valve with a little too much?....

Imo the 0.15 exh valve clearance will be okay to run.

Good Fortune!

Thanks Patton! Time to put the valve cover back on and keep my eye out for some more shims.

on some kz model kawasaki increased the clearance from .1 to .15 in supplimental spec releases, I think urs is included but dont quote me on that, google may turn up this info as I seem to remember seeing this somewhere

Topper wrote:

Which would be better, a valve with no clearance or a valve with a little too much?

Too much is better. Insufficient clearance = burned valve seat and ruined head.

Original spec on mine was .05mm to 0.1mm (which is .002" to .004") but I run .003" to .005". I also think .0.15mm (.006") is OK for an exhaust valve.

Topper wrote:

Thanks Patton! Time to put the valve cover back on and keep my eye out for some more shims.

Somebody on this forum posted that they had some 32mm shims.

kzrider.com/index.php?option=com_marketp...&adid=4375&Itemid=46

bountyhunter wrote:

Topper wrote:

Thanks Patton! Time to put the valve cover back on and keep my eye out for some more shims.

Somebody on this forum posted that they had some 32mm shims.

kzrider.com/index.php?option=com_marketp...&adid=4375&Itemid=46

I've emailed him three times with no response.

Call Z1 Enterprises. They buy and stock used/new 32mm shims. Not sure exactly which sizes they have now, but I have gotten 32mm shims from them before.

I tried them first. No luck. Sounds like I'm ok right now. And that gives me some time to find thinner shims for the next round.