Small Engines (Lawn Mowers, etc.): Onan carb problems, flap valves, loader backhoe

Question
I have a case 646 loader backhoe with an onan b48m motor.  The carb is the type with the built-in passive diaphragm fuel pump (which is not used-vacuum line disconnected and plugged) but I'm using an electric pump.  The problem is that when running it surges and seems fuel starved.  I did a rebuild last year, gaskets only).  The float seems fine (brass, no signs of leakage) but I did notice a ton of crap built up in the fuel inlet body/diaphragm area.  This I believe was from the old electric pump which was corroded. I replaced it and cleaned the bowl and fuel inlet body which has small flap valves that control fuel to the carb.  I believe the float spring was not connected correctly and was not opening the float enough (the spring was kind of free floating) to allow fuel flow into the carb.  I anchored the spring so that there was downward tension on it to hold the float open better. This seemed to solve the problem of fuel starvation, but resulted in flooding.  I noticed there isn't an o-ring in the seat of the brass fitting where the pin which controls fuel flow is located. Should there be one? Could the problem of too much fuel be the fact that even though the float is closing the pin, fuel is still flowing since there is no o-ring to seal it. The mixture screws have little effect on performance or idle.  Any thoughts would be helpful.

Thanks
Al

Answer
your needle seat  seems not to be closing.    and i do believe with an electric fuel pump,  you maybe  putting too much  preasure on it as well.   i,d go back to  the vacuum  pumping system  that belongs on this,   and clean the passages ,and carb.  good again.   there should not have been any thing from  fuel pump getting into that carb,  if fuel  was clean,  and a fuel filter was installed before entering the carb. getting the numbers off of this engine,  and going to a local dealer to get a carb.  diagram  and proper rebuild kid  whould be helpful.