Looking for a little shim guidance

Hope everyone is having a great Friday!!


I am in the middle of a build on a 2007 CRF250R that had a bad crank. I bought it torn down in pieces. Fun fun!!


I have already installed new crank, bearings, and seals. Now I am up top, and have run across a puzzle. The exhaust valve shimes are missing. What would y'all recommend doing at this point? I was think of stopping by honda and pick up a couple random shims to drop in and get a place to start? Any tips or tricks would be great!! I guess I will probably just have to get one of those shim kits with every size there is!


Oh well, I am having fun with it!!


Thanks for any help!



Buy the smallest shims. If they are too big you won't be able to measure clearance

Thanks man. I will swing by Honda in the am.

If the gap is too large for my feelers, is it ok to use two feeler Gage's?

I just see the shims are available in a pretty wide range. 1.2 to almost 3?

No worries!! Gives me a good place to start.

I see those kits on eBay for like $70. Seems like an excellent deal!

Just go to a shop and get some 2.00 shims to measure with. You should be pretty close

I might have a problem, or I am doing it wrong??

I took a 155 shim from my right intake and put it on the left ex valve. I put the cam and rocker in and tried to take a measurement. I was able to get a 3.5 feeler in there. Is it supposed to be light drag? Or "if it fits". Just from eyeball, that 155 shim isn't even flush with the exhaust valve top or above it. (I am sure my terms are all wrong) but, is this maybe pointing to worn out valves?

Can you clarify, is a 155 shim a 1.55 mm?

Usually the intake shims are appx 2mm, exhausts appx 3mm

If the exhaust shim is lower than the seat, you won't be able to get a measurement with feeler gauges, try stacking two of the 1.55 to make a 3.1mm

What exactly is a 3.5 feeler? It can't be 3.5mm that would be much too big. .035 inches?

Thanks for the help!!! And sorry, it is a 1.55 mm shim and a .035mm feeler. And now that I am away from the garage and thinking about it, that decimal point screwed with my head haha.

And yes, the 1.55 mm shim doesn't clear the exhaust valve seat.

I will stack both my intake shims and check again. I just kinda walked away from it this evening. I will check again tomorrow after work!!

.35mm feelwr

Long day


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