CRAP! Need Help, messed up a valve job...

I am an idiot!

Here is what happed while reworking my kz650 head. Had the seats and valves ground and lapped, I got the head back and measured the stem height according the the factory manual shim chart the stems were too tall by .030, meaning the shims required would have been too small. I had the stems resized .030" which when I remeasred the stem height put me right in the middle of the shim chart. I used that chart for the reccomended shim thickness for assembly. Here is the problem, when I re-assembled the head my clearences are way to big... about .030" too big... SHIT!

So I have about .025" too much clearence. Am I screwed here? Do I need to start over with new valves... or is there a way to make up the difference? Are there buckets, or shims that will work. I have 2.40mm to 2.60mm shims installed now, to make this work I would need 3.10mm to 3.40mm

Alright guys let me have it, am I screwed or not?

Maybe you could sink the valves? Or your screwed........

Tyler. maybe, maybe not, stock yamaha application shims only go to 320. there is however the possibility that there are other shims IE (Big 4 dirt) shims which match diameters and are thicker. check your' shims against crf (honda) and yzf (yamaha) and see if you can come to spec. luck g

Tyler wrote:

I am an idiot!

Here is what happed while reworking my kz650 head. Had the seats and valves ground and lapped, I got the head back and measured the stem height according the the factory manual shim chart the stems were too tall by .030, meaning the shims required would have been too small. I had the stems resized .030" which when I remeasred the stem height put me right in the middle of the shim chart. I used that chart for the reccomended shim thickness for assembly. Here is the problem, when I re-assembled the head my clearences are way to big... about .030" too big... SHIT!

So I have about .025" too much clearence. Am I screwed here? Do I need to start over with new valves... or is there a way to make up the difference? Are there buckets, or shims that will work. I have 2.40mm to 2.60mm shims installed now, to make this work I would need 3.10mm to 3.40mm

Alright guys let me have it, am I screwed or not?

The shims for the 750 twins go up to 3.40.
I think the shims for the four cyl engines are still available, you might want to see if you can dial it in. You can go to babbittsonline.com to see what stock shim sizes are offered for your engine.

I would be worried if the valve ends have been over cut, there is a limit on that.

Maybe this will help.


Shim Chart for Valve Grinding

Shim....................Stem Height

#200....................1.494” – 1.496”
#200....................1.497” – 1.498”

#205....................1.493” – 1.494”

#210....................1.491” – 1.493”
#215....................1.489” – 1.491”
#220....................1.487” – 1.489”
#225....................1.485” – 1.487”
#230....................1.483” – 1.485”
#235....................1.481” – 1.483”
#240....................1.479” – 1.481”
#245....................1.477” – 1.479”
#250....................1.475” – 1.477”
#255....................1.473” – 1.475”
#260....................1.471” – 1.473”
#265....................1.469” – 1.471”
#270....................1.467” – 1.469”
#275....................1.465” – 1.467”
#280....................1.463” – 1.465”

You can recut the seats, so that the valve goes deeper into the head and make up for that 0.030''.

About half a year ago I bought a valve seat cutting set on ebay. (from a german shop) for about 130 euro,-
You can use this kind of cuttingtool to cut the seats.

Or you can go to a machine shop and ask if they will cut the seats in about 0.030'' deeper...
Offcourse if you will ever buy new valve's you'll have to ground those also.

You'll have to find out what's cheaper.
Buy a new used head, buying new valves or cutting the seats.. :dry:

Good luck.

I recall last year having a discussion on this forum about making shims, looks like I may just have to try it. Other wise i have to start over on this head again, and that would be a real waste. The valve stems still stand above the keepers, so the shims contact the stem properly, the isn't anything wrong with the valvetrain, other than excessive clearence.

I would rather just replace all the valves. If you cut them that far, they are most likely past their service limit anyway.

another problem with sinking your valves is the compression will be down just a little and youre also stuck if you ever want to put new valves in that motor down the road youll need to spend the money to size the valves the same way again.get ahold of Larry C or somebody who does a lot of head work im sure they can set you up with a good set of used valves to take care of it for ya.better yet maybe send him the head and cams so theres no guessing.

Come to think of it I may even have some valves floating around. I bought some 650 heads just for their shims and buckets. I do know for a fact that I have some 750 valves around. I don't know these small motors enough to tell you if the two interchange.

No sinking the valves is out of the question, no use wrecking a perfectly good head because the valves machined wrong. The vlaves are fine as far as seat contact goes, its just the .020-.030" that was taken off the top of the stem. The stem isn't too short the keepers would contact the shim, the is still some space there, so there is no reason it could not be shimmed to the correct clearences as it is, except for the fact the shims I would need are not available. So I can either take and clean another set of vales I have laying around and grind and lap them and reassemble or I can make soem shims in 3.00 to 3.50 range and be doen with it. The after market shims that Z1 sells are RC40-RC45 and case hardened, I can find a suitable tool steel that I can machine in my lathe to meet that specification. McMaster-Carr sells tool steel rods in 13mm ground outside diameter for $12. I need an emergency collet to make a workholding device that will cost me $20, and it would take a few hours to make what I need. Its worth a try and if it dosen't work I can just start with some different valves. The issue is the valves I have in that head are almost new, the other valves I have have 30 to 40k miles on them.

It sounds like you have a plan. Just wondering how long it will take you to machine, Precision grind, and than case harden the shims you make. The shims must fit in their respective pockets quite precisely otherwise they could come out at higher revs. even with underbucket shims if you get valve float.