Something else to worry about with generators

From my experience, the most gas into crankcase contamination takes place when the engine is stopped. This can be from a stuck float, badly designed carburetor, pressure within the lines and tank, or an uncompleted start cycle like when the engine floods and gas seeps past the rings into the crankcase. A peculiar situation with a crankcase breather and location of the tubing into the air filter might also cause gas in the crankcase. In a multicylinder engine, no firing in one cylinder could cause the above but a user can usually diagnose a cylinder not firing.