adjusting vavles w/ out shims for starting point!?!?!?

Sorry about the subject as it doesn't probably make sense, but I dont know what else to put there.

I got my head back from the shop minus the shims under the buckets :)

I have no idea what sizes they were and no idea for a starting point to begin.

Are the exhaust and intake shims interchangable or specific to each side?

What size(s) would be a good starting point? I do not believe there was a 'standard' from the factory since each part varies, correct?

Bike is a 2000 426 and I will be putting the 450 exh cam in.


Here is what I am running with my 01 YZ 426

exhaust (03 450 cam)

From the shift side 190 & 195


190 -- 200 -- 195

If you don't have alot of shims, hot cams sells a "refill" kit for there shim kits

You get one each of a 180 - 205 for $34.00 That should get you started


thank you much.

Here's what you can do:

It will be easier if you have a reasonable collection of shims to work with, but if you don't, take one in the area of 170-175 and set it on a valve. (sidebar: keep the lifters in the same bore they are in now. Each of them may be very slightly different thicknesses through the top of them)

Set the cam in place and tap the ball bearing down into its saddle with a plastic or soft faced mallet. While holding the cam down with your fingers, check the clearance. If zero or less, go to a smaller shim size and check again.

This will give you a ballpark idea of what size to use. If you are careful enough, you can select the exact size 3 out of 5 times, but ALWAYS double check with the head torqued down and the cams torqued in place.

And thank you too!! That'll certainly be easier than torqueing the caps everytime like I was going to do.

I was about to order the Hot Cams refill shim kit in 1.80 to 2.05mm (5 of each) sizes. I didnt think I'd end up below a 1.80 on either the exh or intake.... I guess I can go to the dealer for any smaller ones if needed.

Grayracer, can you verify the OD on the yamaha shims is 9.48mm?

I don't know the specific size, but a reliable source here once posted that there are two sizes in use on modern Japanese tappet-over-valve setups; one for the 250F's, and one for the 426/450's. If your Yamaha dealer doesn't have what you need, a Honda dealer might have them for a CRF450. 9.? mm sounds about right. The ones for a 250F are much smaller.

can you verify the OD on the yamaha shims is 9.48mm?

yes the 426 shims OD is 9.48 mm

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now