Trying to chase down an erratic idle issue. Pulled the air screw out and I thought there was suppose to be an "o-ring" on the end of it. This has more of a stepped rubber washer. Could this be the issue? I've attached pics as good as I can get. Lemme know. Thanks

 

Not sayin I fixed it but I reseated and cleaned off a tiny burr the little "oring" and it's idlin a lot more consistent now. So hopefully when the rebuild happens it'll be golden.

 

When you rebuild and the opening for that mixture screw is big enough__ a Qtip and some polishing compound (car wax stuff) can possibly clean up what might have burred that o ring.

have done that to more than one needle seat on a carb

WP

 

^^^This^^^

Make sure you get polishing compound and not rubbing compound!!!!!

 

Weird. Any I've seen definitely have a o-ring. Go to CV Performance for parts. Good guys to deal with.

 

Forgive my ignorance. When people say "CV" carb, are they referring to the stock carb?

 

Yes. CV = Constant Velocity. (although earlier EVO's came with a problematic butterfly carb)

 

Is that needle off of a CV carb?

Doesn't look right. The needle valve from a CV has a fine tip to it:



The MoCo started using the CV in (IIRC) 1990, so if this bike is 1990 and newer AND if the carb is still stock, you should have a CV.

Easiest way to tell is to look at the intake. You should see the slide (circled in red) and be able to slide it up like the arrow.

 

He has a Mikuni, he says.

Could the rubber cap be to prevent damage pre-installation?

 

** looking for "nevermind" smiley **