Filing underbucket shims ?

Hey guys,

I have read in the archives that filing overbucket shims is a no no because of hardening, but what about underbucket shims? I have a KZ750e3 (4cyl) and I am very tempted to try this out. Thanks guys, this is the best resource!

I would think the underbucket shims are made of the same material, but can't say for sure.

Why are you so tempted to modify your shims? The safest bet is to just buy the ones you need. www.z1enterprises.com has good prices on shims.

yeah sure, buing new ones is the easy way out

My reasoning is that underbuckets are not directly contacted by the cam and come under less pressure

I have cleaned up light scratches on some shims with some 800 grit sandpaper, atf and a piece of plate glass, hasn't caused a problem. I also think it isn't wise to try to significantly change the shim size by filing them down, it's best to get the right size. Besides thinning the hardened surface, if anything filing would be the wrong technique anyway because the shim surfaces need to be flat and parallel.

Interesting question. If you're one of the few who has the equipment to grind down a shim, why don't you try it and tell us how it worked out.

If I was to try it I'd use a belt sander. On second thought I'd better call Jeff.
Bill

Here's my .02 cents
I agree with savedrider, why would anyone need to even try this? Are they so rare as to be unobtainable? No. These bikes are 30 years old, not 80, so there's no need to resort to making your own parts at this time. There are plenty of KZ parts out there, especially shims.
The guys in the dealer's service dept. were more than willing to swap my shims for what I needed. Only cost gas money to drive there. If I didn't live near a dealer there is the internet and places like Z1 to buy them from.

Yup, there is likely a dealer/mechanic somewere close to you, that will just trade shims straight across, or make some type of deal.

It's a no no. The shims are case hardened. I did it as an experiment. The first few thousandths took forever to lap down. Then it started sanding down quickly.

Also, the cam doesn't hit it directly, but the valve does. If you look at an old 12mm shim, it will have a small wear circle on the side that was on the valve. You could split the shim.

EDIT: oops, I mean 13mm shim.

Post edited by: loudhvx, at: 2006/05/04 21:42

I'm just in the process of getting a bunch of new parts from APE for a customer that used ground 13mm underbucket shims. The damage to the engine when one of the shims collapsed is considerable - and he was lucky.

Totally rebuilt engine with over $3000 of parts and work on the head ALONE. He needed some shims under 2.00mm - the ground shims lasted less than a day. (the bike is a Bimoto KZ1000 running in vintage bike circuit racing)

Why was he lucky? He's been running the bike at 140mph just a few minutes before - he pulled in to do some tuning work when a valve jammed...