01 CR250 Mikuni

Is there supposed to be an o-ring in the air screw? None is shown in the schematic but it seems like there should be one. My carb is leaking fuel all over the lower half of the body and I can't figure where it is coming from. Float bowl gasket is new as is the o-ring on the drain plug. ???

Edited by YHGEORGE

I don't recall.  If there is one, it would be under a small washer, that would be under the spring.  Here is the link to a Keihen on a '96 CR that shows where it is on that carb.  Yours might just be stuck in the hole.


That screw is metering air into the pilot circuit, so there shouldn't be fuel in the passage that it is metering.  That being said, most 2-strokes will have dust on the carb in this area.  Fuel that gets sloshed out of the carb when you tip the bike over (maybe you don't fall? ;)   Anyway, there is oil in the fuel that leaves a residue that the dust sticks to. 


You might want to check your float height.  I'm thinking it is supposed to be 17 -18mm on that carb.  Get your hands on a manual. 


Have fun!


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