valve clearance check with unusal result

1983
kz750l3
24K miles

Something is not making sense-hoping you guys can help me out

Was check valve clearance between the cam lobe+ bucket and got:
Exhaust: .102 .102 .025 .102mm
Inlet: .152 .102 .102 .102mm

Spec is .08-.18

I happend to reread the procedure and noticed a note indicating checking the torque before taking measurement.

The torque on the cap bolts seemed very tight. So I loosened and rest to spec @ 104 in/lbs (converts to 8.67 ft lbs) following the pattern in the factory shop manual.

Inlet side measured same as first time. Exhaust side gap is now too tight to take measurements even with a .025 feeler. I can spin buckets with my finger so I know there is a gap must be greater than zero and less than .025. Loosened up and re-torqued several times with same results.

Any ideas why/how the clearance decreased as the cam cap bolts were tight and possibly over tight to begin with?

I'm confident these are the orginal shims. Is there a standard size these bikes were build with......I'm just tring to save time as I can only work on this on weekend and want to figure out what new shims I need.

Thanks

First of all you don't measure between lobe and bucket, you measure from the rounded base of the lobe if that is what you are meaning. Oil can also change clearance measurements, but dont worry about the changes, just get one main measurement then take out cams and measure shims, don't forget to take notes as you go along. Take notes of measure before removing cams, then on what shims were where then work them out for clearances. And do so much loosening and torquing, that could be more than what was expected for the bikes parts in a lifetime and wear out threaded holes

Puzzling. I'll throw in what I learned:

Be careful torquing the cap bolts. many have been stripped, and many have complained the 100 inch-pound spec is too much. But, that is what's in the manual and it's what I have always used. I happen to have a very accurate (200 inch-pound full range) torque wrench so I can torque them dead on 100 in-lb. Be careful.

QUESTION: did you loosen one both at a time and retighten each? Did you loosen all the caps and then re torque? That may have let the camshaft shift slightly.

On taking the reading: turn the crankshaft with a 17mm wrench in only the CCW direction (don't reverse) and stop when the valve to be measured points directly away from the bucket. Turn the cams a few revs to make sure everything is seated.

Not sure how all the exhaust valves snugged up except to say maybe the cam was loose?

avmedco wrote:

I'm confident these are the orginal shims. Is there a standard size these bikes were build with.

NO

avmedco wrote:

I'm just tring to save time as I can only work on this on weekend and want to figure out what new shims I need.

Thanks

Measure the gaps accurately and write them down. Note the ones that need changing and by how much.

Take the shims out (can be done with shim removal tool) one at a time and measure with calipers (don't assume marked value is right and many have the marks worn off anyway).

You will be able to calculate the shim you need at each location. In some cases, you can swap shims around and get a couple right and end up only needing one or two new shims.

Take the shims out (can be done with shim removal tool)

Umm, nope, no such tool will work on a KZ750L3, it's a 750 four and the shims are under the buckets. You have to remove the cams in order to get the buckets out to remove the shims that are stuck to the inside of the buckets (held there by an oil film).

As to the original post, the bike has 24k on it, the clearances were in spec when you originally checked, and I bet you regret messing with the cams now

If it ain't broke, don't mess with it


I'm going to have to give this some thought to figure out how it can happen.

Are you working on the bike while it's on the side stand?

Yes-Measured from rounded base and bucket

Loosened all the end cap bolts and re-torqued per pattern and specs in factory manual.

Usually I don't mess with things when they meet spec. I was going to have to pull the cam anyway as the one exhaust measurement was way out of spec.

Bike is on it's center stand.

bountyhunter,
you said turn it CCW, counter-clockwise..did you mean to say turn it CW ? clockwise?
I think that's what you meant... :whistle:

OKC_Kent wrote:

bountyhunter,
you said turn it CCW, counter-clockwise..did you mean to say turn it CW ? clockwise?
I think that's what you meant... :whistle:

On my 750, I believe the correct (normal) rotation of the crankshaft is counterclockwise as viewed from the right end (under the timing cover) where the 17mm nut is that allows turning of the crankshaft.

I noticed when setting my valves that because there is a little slack in the cam chain, as you turn it the chain is tightening up to pull the cams against the springs in the valves. That basically pulls the camshafts down fully against the lifters. If I reversed the direction of the ctankshaft and rolled it back a bit, that allows slack in the chain going across the top. I noticed a couple of the valve clearances changed a little (like maybe a thousandth). I believe it's because the chain tension was released and it allowed the camshaft to rise up slightly because of the small amount of play in the cam bearing journals. I think to get both consistent readings and the TIGHTEST reading on clearance, you need to rotate the cam slowly and stop the cam without reversing direction. Not critical, but it gave me more consistent readings.

steell wrote:

Take the shims out (can be done with shim removal tool)

Umm, nope, no such tool will work on a KZ750L3, it's a 750 four and the shims are under the buckets.

Oh, it's one of those......

bountyhunter wrote:

steell wrote:

Take the shims out (can be done with shim removal tool)

Umm, nope, no such tool will work on a KZ750L3, it's a 750 four and the shims are under the buckets.

Oh, it's one of those......

Yep, and it's also one of those that rotate in the clockwise direction

The twins are the only ones that rotate counter clockwise (as far as I know anyway).