yz450f rebuild question

I have just about finished rebuilding my top and lower end on one of my 03 yz450s. it seams like it doesn't have any compression when i kick it over with the cams in. if i take the cams out. the bike has plenty of compression. i know there is the decompression exhaust cam, it seams to be moving smoothly. the bike is so easy to turn over you cant tell when it is at the top of the stroke. it just moves smoothly through everything.

I just complete finished rebuilding my other 450 and had no problems at all. i was going to try to swap the cams from the other bike, but figured id ask before i did that. i only rebuilt the engine because of hours, the engine would start 1st kick every time when i pulled it appart.

any suggestions?

Double check your cam timing and valve clearances. The auto decomp unit relieves compression from the first 2/3 to 3/4 of the compression stroke. If you have a tight valve or your exhaust cam is retarded, you'll lose the whole of it.

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