..spf...From my experience, what you're finding in the air filter compartment is most likely a fuel / oil mix...however, if you are having carburetor problems, or you're "flooding" it while you're cranking, some additional fuel might find it's way in there also..there is also a small "clear" tube beneath the compartment that is plugged on the end. This is your crankcase vent. You should drain that tube periodically...Also verify the integrity of your air filter, and that it's seated properly, and the seals are in good condition...
..there may be a problem with your "Auto Bystarter", (electric choke) which is mounted on the side of your carburetor...Though, usually a problem there would cause the engine not to start initially...I would suggest getting some good spray contact cleaner, or carb cleaner...remove and dis-assemble your carb, (remove the Auto Bystarter too), and thoroughly flush ALL the ports (there are many ports) ...work the throttle body, and accellerator pump when spraying into those ports...
..maybe this will help...it did for me when I had a similar problem...
peace