Random Carburetor dripping seeping drooling

Leaking carb bowls come from a couple of things. One is the bowl gasket,  heavy floats that sink allow the fuel level in the bowl to rise too high, improper brass float armature out of adjustment allows fuel level to be too high and last the needle valve is not completely sealing off down inside its brass receptacle.

So since you are saying it's coming through the air filter it isn't a gasket issue, but could be any of the others. What was your float weight? It needs to be under 7 grams as a pair. If these are okay then check the brass float armature measurement. If this is off then the fuel level can rise until it spills back out of the carb throat as you described. If this is okay then it's most likely the rubber tipped needle valve not completely sealing.

Plus if this is a high wing you need to shut the fuel off after your done flying everyday. Failing to do this can cause a small leak at the needle valve because you always have head pressure if you have a high wing. Gravity and fuel weight is at work.

I had this issue on a low wing plane. The fuel doesn’t siphon during engine off times but this is what I experienced. When I would turn on the electric fuel pump and get distracted for a few minutes before starting, the engine would start real rough. After 30-45 seconds it would smooth out and run fine the whole flight. This happened a couple of times before I traced the roughness to the right carb dumping fuel into the intake causing the right side of  the engine to be very rich. I cleaned the bowl, checking float bail adjustment, etc several times and the problem still occurred. My solution was to replace the needle valve on the float. I actually changed both. The problem has never returned. 

Thanks Roger and Walt. Carb bowl gasket is good, no evidence of leakage around the bowl exterior. Float pair weighed 6.39 grams on a calibrated scale. I didn’t measure the float cutoff but rather held the brass arms horizontal and turned the fuel valve on. No leakage observed. The leak occurred with the aircraft sitting overnight in the hangar and no fuel pump had been operating for days. It is a high wing aircraft. I had a half load of fuel (five gallons) in each wing tank, my standard load since new. Upon inspection and reassembly, the leak stopped, with the same fuel load. There’s nothing in any Rotax tech manual regarding closing the fuel tank supply valve if the aircraft is a high wing configuration to prevent carb bowl leakage that I can find unless I’m missing something? In any event just taking things apart and checking their function then reassembling them fixed the problem. Same as the previous event long ago. So if the float shutoff valve has deteriorated and the fuel load is unchanged it should continue to allow the bowl to overfill yes? But it’s not now. It’s just puzzling.

§ 23.995 Fuel valves and controls.(a) There must be a means to allow appropriate flight crew members to rapidly shut off, in flight, the fuel to each engine individually. (2) Allow appropriate flight crew members to reopen each valve rapidly after it has been closed.

Attached is from a Cessna 150 POH

Cheers

Jim, sorry, dropped my text to accompany the POH and CFR context.  Yes it is common practice to have a fuel shut off an an aircraft.  I would be sure that when you are in a hanger for sure you want it shut off to prevent exactly what you have noted.  Fuel on the floor is not a good thing.

Cheers