CRF 450 How to adjust the valves

I have a 03 450 that I just got and it runs great! I love my bike and am big on preventative maintenance. I have searched the threads on TT and have not found any descriptive threads on how to check valve clearance or adjust them. Just by looking at them, I can see that the intakes need to be shimmed and the exhaust valves can be adjusted quite easily unless one needs to be adjusted differently than the other.

I tried to do it last night, and lined up the marks on each side to get the piston to TDC to check adjustments and could not get any readings on tolerances on either the intake nor the exhaust. I moved the crank a little bit forward and got a .011 reading on the exhaust valves. I read in a thread that the spec was .011" for the left one and .014" in the right for the auto decompressor. The spec I am using for the intakes is .006" Are these specs correct? :excuseme:The only issue is that the adjustment for the exhaust valves is one and the same. Different from my KTM where you can adjust each valve individually.

No matter where the cam was on the intake valves, I could not get any readings. Does anyone have a thread, website, downloadable manual, or article on checking and adjusting valves in these beasts?

First off... Use the manual. But here goes...

Both intakes should be .006 +/- .001

Both exhausts should be .011 +/- .001

If you need to adjust you're going to need a shim kit (or you buy your own shims separate.) If you have .004 clearance and you need .006 look at what shim you have, and then go down 2 sizes because each shim is in .001 increments.

If you have .012 and need .011 go up one shim number.

I'm assuming you know how to measure clearances. And I'm assuming you know how to take the cam off and put the new shims in. Other than that... You're on your own. I just did it last weekend and it wasn't too hard, and I'm reshimming again in like five minutes so... Any questions, ask.

If you can't get a reading on the intakes, they are probably pretty tight. Soon the bike won't start anymore :cry:. If the clearances have gone to zero you may be in for a valve job pretty quick. :lol::cry:

Adjust early and often to avoid frequent valve replacements. Valve replacement will probably be sooner than you think :cry:

Note: when you do end up getting your valves replaced, :lol: Consider Kibble White stainless valves and spring kit. I bought mine here at ShopTT. At replacement MAKE SURE the valve seats get cleaned REAL GOOD and the new valves are lapped in real good. :cry:

Those that skip the cleaning and lapping are usually in trouble again real quick.

The CRFs have valve problems :cry: but staying on top of it will ease the pain.

I have the head apart on my bike right now doing the valves. Anyone know if the shims can be different sizes on the two intake valves?

I have the head apart on my bike right now doing the valves. Anyone know if the shims can be different sizes on the two intake valves?

yes they can, valves don't wear the same

Help I can get 0.20 in my intake shims on both sides is this bad ? Do i need change then or thay fine? It's a crf 450 05

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