as a 30+ year motorcycle mechanic i can tell you the following. #1 always turn off your fuel when not riding.even when the bike is brand new because the the fuel can slowly leak through your needle and seat in the carb and either fill up your crankcase with fuel or your air filter. #2 make sure you have an inline fuel filter between the tank and carb as all it takes is a very small particle of dirt to make the needle in your carb stick and fuel to leak everywhere.if fuel is already coming out of your air filter make sure you have an inline filter and remove the bowl from the bottom of the carb disassemble the float,and needle assy clean it with a good quality aerosol carb cleaner and reassemble it.warning DO NOT USE COMPRESSED AIR TO BLOW IT OUT small o-rings and seals can go flying and you will never find them.if this does not solve your problem you could also have a bad petcock which is not completely allowing the fuel to stop flowing even though you turn the fuel off at the tank.if neither of these works it is possible that the float is out of adjustment but not probable as most floats today are plastic and you cannot adjust them.hope this helps you.thanks,allen