Weird valve clearances?

polkat wrote:

Well, here's what is also weird. I understand shims were made in .05mm increments, but when I measured the shims before I reinstalled them, I got some weird numbers like 2.54mm (three like that), one 2.59mm shim, a 2.56mm, a 2.64mm, and two 2.48mm's. My measuring technique is accurate (a good quality millimeter caliper). They look good (not much visable wear) but that doesn't sound like original factory sizes to me. If I need them, where can I get individual shims?

Also, I may not have always put the same side of the shim against the valve stem when I reinstalled. Would that make a difference (doesn't seem so)?

Lastly, I have found several shim buckets that spin fine when installed, but are quite difficult to remove from the head. Is there a trick to this? Thanks!

I have some used shims that do not measure as they are marked, and dont look to be worn, I suspect that there were some tollerances during the mfg process.

Also possibly someone ruined a shim by "grinding" it down, which destroys the hardened surface and weakens the shim, making it prone to break.

Usually a good idea to install the shim with number side down against the bucket and away from the cam lobe, whereby the number won't be worn away by the cam.

Good Luck!

Also, cheap digital calipers are not accurate. That leads to inaccurate readings.

Shims are not always the Exact size as marked. They may be as much as .03mm down or .02mm up. Always install the shims with the etched number down into the bucket. This way they will cup only on one side and you will always be able to read the #. If you don't ride at or past redline all the time, it is OK to have the gap .01-.03 larger than specified. You will only have a tiny bit of extra hiss in the engine. If your valve springs are more than about 15 years old than the extra gap is irrelevant. Having a little more gap is OK having a smaller gap is very bad.

Sorry, I thought I included the bike type. My fault. It's a KZ750H3 750-4. The caliper is an older mechanical type and I had it's accuracy checked a few years back. It was right on. Thanks for the replies.

Any suggestions for a bucket that won't come out? I pulled the buckets off again last night and exhaust one's bucket is stuck hard.

Liquid wrench, or the like, to remove the bucket.
Try your best not to mark it up.
A real strong magnet might work best.

GL

TeK9iNe wrote:

Liquid wrench, or the like, to remove the bucket.
Try your best not to mark it up.
A real strong magnet might work best.

GL

Yes a strong magnet works the best.

Thanks for the tips! I've got a real powerful magnet (from a guitar amp speaker), but it won't even budge it. It's jammed in somehow. It will move up and down from the cam lobe, but higher then that and it jams hard (oddly, it wasn't that hard to put in). I think that somehow it became a little out of round.

I'm afraid I might have to drill a little hole in the top-near the side so I won't hurt the retainer, then grab it with a screw. Of course, I'll have to replace the bucket but I have no idea where I might find a single one. Any other ideas?

Finally got the bucket out. Thought I'd post how I did it in case someone else stumbles into this problem. I found a small bolt with a very smooth head (and smoothed it some more with 400 paper), then using a super glue called Q-Bond (about the strongest you can find) I glued the bolt upside down onto the bucket. I let it cure, then rigged up some wood so I could pry straight up with some big needle nose pliers. You have to pry straight up (in line with the bucket) and not to the side, as the glue has good tension strength but lousy shear strength. Eventually it came out.

Then you can knock the bolt sideways and it will pop off without damaging the bucket. The remaining glue scrapes and cleans off easily with acetone.

Now, I measured the bucket diameter....and found it to be about .05mm wider then the rest. What? How can that happen, and why wasn't it a problem when someone did the last rebuild?

Guess no one but me noticed Patton... :laugh: :laugh: :laugh: :laugh:

larrycavan wrote:

Also, cheap digital calipers are not accurate. That leads to inaccurate readings.

That's a good point. You have to zero them over and over and you have to squeeze them together like you gotta pair. Try measuring valve stem spec's end to end without closing the caliper tightly. BAM! Your late for dinner.