Small Engines (Lawn Mowers, etc.): Oil seal popped out, crankcase pressure, vacuum gauge

Question
What will cause a drive end oil seal to pop out on a B%26S 18HP Twin vanguard working on a riding mower. Compression 125 %26 150 on cyliders.

Wayne

Answer
Brand new engine?  If the engine is a few years old then rule out manufacture defect.

This leaves either a wore seal or crankcase pressure, maybe a combination of both.  Is the valve breather working correctly?  Any engine gaskets, dipstick o-ring or dipstick tube rubber gasket leaking preventing the engine from maintaining a vacuum?  

Do you have a vacuum gauge to check engine vacuum?  Don't need a fancy gauge...all you are check for is that the crankcase holds a slight vacuum?

Let me know.

Eric