What would make a 4.5 hp briggs n straton push mower blow out all the oil when you start it.?

(2011-12-06 15:20:22) 1. David Says: it will run when primed for a few seconds but blows all the oil out the exhaust. sounds like rings are bad to me. how much might it cost to fix? it was given to me so i don't want to spend alot to fix it.2. gee-man Says: broke ring or the head gasket.3. Hardy J Says: On the side of the block you will find a breather valve for the crankcase. It is held in place by two screws. A tube runs from it to the carburetor. Replace this valve and you should be ok.4. Fox Riley Says: I'd say its the exhaust valve stem seal, no idea how much it would be to replace but the parts are very cheap so if decide to fix it yourself then should be pretty good. Tag: What would make a 4.5 hp briggs n straton push mower blow out all the oil when you start it.?