I have a Craftsman rototiller that will not stay running. When I take the airfilter off I see oil and or gas below the air filter. Is this normal?

yes that is normal the air filter is connected to the carb and is how it gets air to the engine, to get it to run good take off the carb and clean it with gas, and change oil and clean the oil filter check if you need a new spark plug and clean all bad gas out of tank.