valve break in

is it normal for a valve to change slightly in clearance during break in? i have a 2007 yz250f that the center valve was near to tight from the factory and then it tightened after engine break in at 25 hours. very very little it tightened. tightened just enought that i couldnt get the feeler gauge under it but the next feeler gauge down was very loose. i shimmed it and there are no signs of it moving. is there a chance the engine break in was the cause of valves to seat and change and tighten slightly? or do i have a defective center intake valve?

If it it's not moving, it's fine.

but just the fact that it did move a little during break in? does that matter?


This can happen, it is rare though. If it keeps moving then you have a problem. If it moves a little, then stops then the valve was just settling.

I'd think a little wear-in is normal, like maybe a thousandth or two over the 25 hours you speak of. But if it keeps moving then yes it's a problem.

whats the chance of a bike with a perfectly clean air filter and change of oil every 3 hours having a bad valve?

I had that happen to one of my exhaust valves, it moved once after 2 months of having it but never moved. 190 hours on the same exhaust valves, clean filter and oil change every 5 hours is all i do. the intakes were a different story, they only made it to about 90 then 90 again

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