Lots of things could cause it. Excessive fuel pressure (no more than 5# needed), a heavy float in the carb and the fuel is bleeding over, a choke stuck partially on, a bad fuel pump diaphragm leaking fuel into the crankcase, and over time, even a weak ignition system or a poor tune up. (a hot spark and complete combustion is what you need)
Look for the carb issues first. They are your likely culprits. Change that oil and filter before you do bearing damage.