Carb Issues

[SCguy]

Okay, having a few issues with my truck.
89 Mitsu MM 2.0 AT
Truck bogs down under acceleration, especially around 45-50 mph and kicks out clouds of black smoke, running way rich. The truck also will not rev over what I'm guessing to be 2500 rpm (no tach). The thing is, that with the air cleaner off , the truck runs great, no hesistation, no running rich, and free-revving. The problem is not in the air filter. The truck bogs just as bad with the air cleaner on, but without air filter.

Did a bit of digging on iATN, and performed a recommended test for the above symptoms. The test was to take the hose off of the charcoal canister marked 'Carb' and lightly blow into it with the motor idling. According to the test if the engine stalls, it indicates that the bowl vent valve is not functioning properly. I tried it, and the truck stalled quick and hard.

My question is, is the bowl vent valve serviceable? If so, does fixing it require the disassembly of the carb. Would it be included in a carb rebuilt kit? And lastly, what exactly does the bowl vent valve do? If it is just a check valve, couldn't I just splice one in the vacuum line?

Thanks,

RD

[Ramit]

I do not believe that they are serviceable,and no, you won't get one in a rebuild kit.I'm guessing that you are dealing with the factory Mikuni carb.Basically, all it does is allow the gasoline vapors to go into the charcoal canister only when the engine is not running.With the engine running,I believe the electrical switch senses vacuum or oil pressure and closes the bowl vent off.You shouldn't have to disassemble the carb to remove it,but it would probably be easier to remove with the carb off of the engine.Go to www.carburetorexchange.com.They are in El Monte,CA.They have helped me in the past. Good luck!

[camoit]

I would check to see if the float is sunk or needle and seat have junk in it. The fuel is just running in as fast as it can.