2003 YZ450f post rebuild troubles

Hello, afew eeeks ago i bent 3 valves and thus having to do a bit of a re-build on my bike. anyway i put in 3 new intake valves, all new guides & seals. also, a new cam-chain and cam-chain tensioner. i should also point out that earlier this spring i put in a new piston, rings, and cam chain as well.

anyway after i got the valves put in and this and that, i put it all together, took it for a ride and the thing just isnt what it used to be, power-wise. i took it for a short ride and wasnt impressed, the thing wont wheelie, and its lacking big time in the power department. it runs like a top and the motor is tightet than a ticks ass, but im dumbfounded and dont know were i went wrong..any ideas? if u got a question ask it, i need some help! thanks!

> When your old cam chain slipped, it was because of seizure. The sprocket on the cam that seized slipped because of it and is out of time, even though it says it is.

> You didn't time it right.

:excuseme:

> When your old cam chain slipped, it was because of seizure. The sprocket on the cam that seized slipped because of it and is out of time, even though it says it is.

> You didn't time it right.

I would say timing, too, but if it's right and you've double checked it...

Did you replace the piston and rings this time? I assume the valves bent from contacting the piston...could the piston and/or rings be damaged, causing a lack of compression? Maybe drag from a dicked up small end, big end, or crank bearing? How did they feel when you had the motor apart? Slipping clutch giivng the feeling of being down on power?

The timing is perfect and the cam didnt slip, im positive on this and am too tired to go into details. that being said, the clutch is acting up (ie. engaing itself when lever pulled in ) but it definatly isnt slipping, maybe up top a bit but i doubt it. myself and my father both are under the impression im losing compression somewere. all the bearings / clearences in the bottom end were checked and were perfect. the motor is running like a top and is as tight as a ticks as, just deosnt have the snap it use to pre-rebuild. are next step we figure is to replace the piston and rings, but we are still unsure.

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