yz250f idles very rough even after cleaning the carb and jetting

I'm working on a 2004 YZ250F that a relative has picked up from someone recently. It has major idle problem's with out the choke. The carb is absolutely spotless and every passage squirts a good flow carb cleaner, especially the idle circuit. The fuel is fresh as well. This carb has a power wing plate welded in the intake side. I have tried jets ranging from 38 to 52 with no significant change in performance. I am at almost full idle with the adjuster to get it to roughly idle without the choke. Once again the pilot circuit is 100% clean. I have verified the valve clearances are good, the timing is good and leak down is good. I am stumped. Any ideas?

Confirm the slide vacuum release plate is in good condition and not in upside down.



Someone epoxied the power wing in (you cannot weld diecast)? That'll screw up performance. Another case of s'slowed down for racing'.


The slide plate is in good condition and is installed correctly.

Edited by kdsd731

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