Small Engines (Lawn Mowers, etc.): Oil blowing out of exhaust?, mud dauber wasps, oil pressure switch

Question
I have a Craftsman High Performance 19hp Kolher Courage riding lawnmower that was working fine last fall. I drove it into the storage shed last year and it had NOT been used all winter. Today March 20, 2011, I attempted to start it up and us it the for first time this season. After stating, the engine would only run a short time and shut off, it did this two times, so I checked the fuel and topped it off, checked the oil level and it was fine.

Started the engine one more time, and again after running a short time the engine shut off, this time I noticed lots of smoke coming from the exhaust. There was also some smoke coming out of the exhaust the two other times, however I just thought the some was because the engine had not been run since last fall. On closer inspection I noticed lots of oil coming out of the exhaust and a buildup of oil under the front of the engine.

My guess is something is wrong with the internal part of the engine, causing oil to escape with the exhaust and the oil pressure then drops and the LOW oil pressure switch kills the engine.

I have also read about a blocked breather causing a similar problem, there have been mud-dauber wasps in the building?

Again, the engine was working fine the last time it was used.

What could the cause be for this type of failure, the oil to be coming out of the exhaust and the oil pressure dropping?

Craftsman High Performance with 19hp Kohler Courage
Model No:917.275180
Serial No: 062405D01212074

19hp Kohler Courage
Spec. no. PS-SV590-0004
Family: 5KHXS.5972GB
Serial No: 3515100083
Serial #: 3515100083

Answer
You can download the engine service manual from Kohler.  The link is below.

http://www.kohlerengines.com/manuals/landing.htm

I would start by checking the oil level and see if it smells like gasoline.  If so, then gas has leaked past the carb, the inlet needle, and into the engine.  We see this a lot when engine sit over the winter.

If the level is correct and does not smell like gas, then I would see if the crankcase is holding vacuum.  If the breather is not functioning properly there will be no vacuum and oil will get past the piston rings and valve.  The engine either has to burn this oil or push it out the muffler.

The repair manual will tell you how to repair the carb, if required, and how to check for crankcase vacuum.

Let me know what you find.

Eric