I have a '93 softail custom with a overflow problem out of the bowl vent tube, before anyone tells me it is a simply float adjustment let mem very emphatically state it is not the float !!!!!! The float has been adjusted several times by several people. We have even removed the Mikuni and replaced it with a freshly rebuilt CV, and the CV is worse than the Mikuni. Anybody have any suggestions?

 

I am finding also that I still hate carburetors, lol. With your issue carrying over to a different carb, my only thought has to be the fuel supply. Could that some how be excessive? Too much pressure from pump? Maybe check that somehow to verify correct psi. Just a thought!

 

Mines a gravity feed. It also has a new set of gas caps on it to make sure it's venting through them properly. That was a grab at straws since it primary does it after it's set for awhile.

 

Then maybe rebuild the float valve? I would suspect that its just not shutting off properly. Maybe has a damaged needle or crap in there?

 

The CV has a new one in it and it's worse than the Mikuni

 

next time you stop , loosen,leave the caps loose
see if problem goes away?
if so go through the tank vents/crossover line,etc.


sounds like the tank is pressuring up