Small Engines (Lawn Mowers, etc.): John deere stx38, blue smoke, white smoke

Question
My J.D. STX38 with a koehler 13 HP all of the sudden quit when I was cutting the lawn.  After it cooled down, I restarted it and it was blowing white smoke out the exhaust.  Sounds like a seized ring or burnt valve but.... When I start it up, it runs fine for about 5 minutes, then starts to blow whit/blue smoke.  Is it cooked?

Answer
Have you checked the oil? I'm guessing you will find it way overfull and smelling like gasoline. If this is true, you have a needle in the carburetor that is not seating, allowing the gas to run through the breather into the engine and thin the oil out. If it hasn't been run too much it should be ok, just change the oil and rebuild the carburetor.