Small Engine Troubleshooting Problems? Ask a Mechanic Now.
The carburetor needle valve and float did not shutoff the fule coming from the tank, and flooded the carburetor and went into the crankcase vent, into the oil. Repair needs to be the oil change, and the needle valve and seat and float checked. Or carburetor replaced. If I owned it, I would install a fuel shutoff valve in the fule line from the tank, and keep fuel shutoff between uses.
What is the engine model number? Not shown with mower model number.