Why does my mower blow white or blue smoke when it is running?

Why does my mower blow white or blue smoke when it is running?
The simple answer is that your engine is burning oil. This could be caused by over filling the engine with oil, turning the mower on its side, or worn piston rings. The most common problems that we see are customers over filling the engine with oil or turning the mower on its side.

In the case of over filling, the excess oil is forced out of the crankcase through the breather by the movement of the crankshaft, piston, and rod. This oil is then sucked into the carburetor and eventually burned by the engine.

When a mower is turned on its side with the carburetor facing down, the oil from the crankcase is allowed to pour straight into the carburetor and muffler. This will cause the engine to smoke very badly and, in some cases, will clog the carburetor bad enough to require it to be removed and cleaned.