Small Engines (Lawn Mowers, etc.): 12.5 hp B&S model# 286707, crankcase breather, head gasket

Question
My Engine is burning alot of oil. It is gumming up on the spark plug. Now it will not crank. Somebody said it could be Piston ring or valve stuck open. The mower is a 1990 Snapper I only paid $154.00 for it. I am willing to spend about $100-$150 on it. Any advice would help!

Answer
This is what I would do.  Drain the oil.  Inspect the crankcase breather.  If it is full of oil replace it and the gasket.  If ok check the dip stick o ring and the oil fill o ring for a good seal.  Check the crankcase gasket for leaks and the oil seals. Replace the head gasket and the spark plug.  Put new oil in the engine and test run.  If this is all ok replace the short block or discard the engine.  

What I think it is, is positive pressure in the crankcase.  When this happens oil is pumped through the breather into the sir filter and the carburetor or into the valves through the valve stems.  The valve stem guides are not replaceable on this engine.  If it is none of these the cylinder is probable worn beyond repair and not worth the cost of resizing and the parts.  Hope I helped