KZ650 valve clearance wierdness

I'm checking the valve clearances on a 78 KZ650 and 3 are out of spec. I order 3 of the proper size, install and check all of them again. I got completely different measurements across the board! One valve went from a .08 clearance with a 235 to a .20 clearance with a 230. Another valve that went from a 245 to a 240 stayed the same. What the heck is going on? This happened to me the last time I checked the valve clearances on this bike and had to do it 4 times until I had them in spec because they kept changing. It was warmer than when i checked them initially but maybe 15F degree difference tops. i suppose that would effect it some because the shims i did not change or even touch were any where from .03 to .05 tighter than when i first checked them. Any tips? I don't want to have to deal with taking the cams in and out 4 times again.

New or used, shims marked with the same # will very ever so slightly. This can actually help you if you have several shims of the same #. One of them might be the Best fit.
Otherwise, do it on a cold engine as that is the spec. If in doubt, rotate the motor over by hand another rotation and recheck the same valve. You can use the chart thats in "File Base". Take a complete measurement of all of them, go back and double check it. Then make the adjustment to 1 valve at a time, rechecking as you go.

Your numbers sound within the realm of tolerances of the various items involved, such as the shims the feeler gage,the operator the amount of oil on the shim or bucket etc... :ohmy:
However I wouldn't adjust and re-check 1 at a time..This is why people talk about stripping out the cam cap screw threads..
If I've checked them twice and I usually check 4 or 5 times, Then do the math, get the shims needed(verify the thickness with calipers,as this is often part of the problem, the shims not being as close to the stated thickness as they should be) and put it all together 1 time..follow the procedure in the FSM for making sure to seat the shims.... Check the clearances several times, kick it over a few times and check again.... I've had very few that have required taking the cams back out...... Sure it might happen but so might a lot of things

What do you mean adjust them one at a time? they are shim under bucket so i have to remove the cams to get to the shims. if I'm doing that, I change all the ones that need to be changed because its kind of a PITA to pull the tensioner, idler, cam caps, then cams, then do that in reverse to check for each one. I checked them all probably 3 or 4 times because I have had this problem before. The bike is dead cold and has been sitting for over a week. When i referred to the temperature i was talking about the ambient air temp being 15 degrees warmer the second time.

I guess maybe my shims aren't close to the stated thickness. but this doesn't explain one of the shims i did not touch changing a whole 0.10mm. I found a place that will sell me shims locally, so i guess ill go down there with a caliper and measure them for the ones i need.

They aren't too far from spec but i LOVE how smooth this engine is when they are dead on. soooo easy to start, not even half a kick and it will start.

Just a thought....This bike has 82,000 miles on it. I believe that to be the correct milage, it has been VERY well maintained its whole life. great compression. Im nearing the low end of the shim spectrum and was told it is because my valve guides are"bedding in" could this have something to do with this? Another member on the KZ650.info site said he had similar problems on a head he freshly rebuilt.

With mileage the valves pound into the seats and "reseed" into the head, and the clearance goes away as the valve moves closer to the cam. Changing to a thinner shim restores the clearance but at some point you run out of "thinner" shims. When a valve job is performed material is removed from both the seat and valve face, thus the valve moves deeper into the head as well, which is why a proper valve job includes skimming some material off the end of the valve stem to restore some of the lost clearance.

As for inconsistencies in the measured clearance is concern, the cam positioning method has an affect on this. For example, if you use the simple method of pointing the cam lobe away from the valve before measuring clearance, the adjacent valve will likely be pushing up against the cam and skewing it within the journal clearance. Measuring the valve then will result in the maximum amount of clearance possible. If on the other hand you position the cams like suggested in the manual, then the adjacent valve will be on the base circle and the clearance will be less than using the method detailed previously, because the valve won't be pushing up on the cam. I don't know if this explains the situation at hand, but it bears mentioning.

Exactly........

To the three previous post, that is

DoctoRot wrote: I'm checking the valve clearances on a 78 KZ650 and 3 are out of spec. I order 3 of the proper size, install and check all of them again. I got completely different measurements across the board! One valve went from a .08 clearance with a 235 to a .20 clearance with a 230. Another valve that went from a 245 to a 240 stayed the same. What the heck is going on? This happened to me the last time I checked the valve clearances on this bike and had to do it 4 times until I had them in spec because they kept changing. It was warmer than when i checked them initially but maybe 15F degree difference tops. i suppose that would effect it some because the shims i did not change or even touch were any where from .03 to .05 tighter than when i first checked them. Any tips? I don't want to have to deal with taking the cams in and out 4 times again.

I have a couple of valves that will change clearance based on cam chain tension. There is up/down play of the camshafts in the journals and if I revers direction on the crankshaft nut while checking (and release cam chain tension) the clearance would change about .002" on a couple of valves.

For consistency, make sure to turn the crankshaft only forward and don't reverse direction when checking.

ALSO: the cam cap bolts do strip easily. I recall the spec is about 110 inch-pounds maximum but do not push it, 100 I-P is enough. You must have a low range torque wrench. I recall the one I got at Harbor Freight is 200 Inch-pounds full range so it can do 100 I=P very accurately.

Well i got it sorted. Don't know why the tolerances were changing, perhaps operator error, temperature, shims not being the correct size. still cant figure it out. I always check by moving the engine forward and use a high quality inch pound torque wrench for the cam caps set to 104 per FSM.

Bountyhunter wrote: I have a couple of valves that will change clearance based on cam chain tension. There is up/down play of the camshafts in the journals and if I revers direction on the crankshaft nut while checking (and release cam chain tension) the clearance would change about .002" on a couple of valves.

I am a bit surprised that there is up/down play in the camshafts......I didn't think there should be any play at all, am I missing something here?

bluezbike wrote: I am a bit surprised that there is up/down play in the camshafts......I didn't think there should be any play at all, am I missing something here?

There is clearance between the cam journal OD and the ID of the cam caps and head. The cam wouldn't rotate otherwise.