Export thread

What would cause an engine to run approx. 2 minutes , building up so much crankcase pressure that the oil is forced from the crankcase up through the case vent hose into the air filter housing and spraying the oil into it's surrounding ?

Crankcase breather valve is bad,i guess.., post the engine model and spec numbers so we can see which 12.5hp engine you have.

mod 405002x8

We need the engine model. It'll be stamped above the spark plug most likely.

Mod 28V707 , Type 1113-E1 , Code 020321ZD

Usually this happens when the head gasket is blown or the float valve ails & the sump is 1/2 full of fuel

28V707-1113-E1 L Head engine.

Or an L head (side valve) engine with a badly worn exhaust valve guide and back pressure from the exhaust. OR simple lots of blow-by pass the rings.