Frank - need to askl if you use the fuel line to the carb for filling up. For inverted engines try to use a 2 line system, if the carb is exposed then use the fuel line to the carb to re-fuel. If not then use a re-fueling valve. After you have fueled up DO NOT prime the engine. Just start it with an electric starter and it will not be so prone to flooding. Also, make sure the throttle is always in the low position.

I have run 4C and 2C engines inverted and I hardly have problems, I do not re-position my tanks, its always stock.