Presurized Crankcase

JazzDad · Jun 29, 2018

I called Briggs and Stratton, and must have gotten today's new hire. (In the past, these folks had been very helpful.)

Got a mower given to me. It had sat up for years. Cleaned the carb and got it running. Engine had run for about 30 minutes, when oil began spewing out the filler/ dipstick neck. The dipstick was in place, and the gasket intact. I looked on the 'Net and found bad head gaskets to be a frequent culprit on these small OHV engines. (Combustion gasses leak from the cylinder into the valve chamber.) I examined the head gasket, and can't see any breach. Now I'm wondering if there is blow-by on the rings. Compression test yields hardly any reading on the gauge. And yet the engine starts easily, seems to run strong, and does not smoke.

Do I try the easy item first - the head gasket - or tear it down to look at the rings? (The cylinder wall is not scored at all.)

CobyRupert · Jun 29, 2018

JazzDad said:
Now I'm wondering if there is blow-by on the rings. Compression test yields hardly any reading on the gauge. And yet the engine starts easily, seems to run strong, and does not smoke.

Just how easy does it pull?
Dipstick smell like gas?

JazzDad · Jun 29, 2018

No fuel in the oil. It pulls very easily, but yet it runs well.

Only complaint is the oil blowing out. The engine can't last long that-a-way.

More reading is leading me to think the breather is malfunctioning. (Never seen a bad one in my years of piddling around on these engines. And why would it suddenly stop working?) I will check that tonight.