Small Engines (Lawn Mowers, etc.): Engine wont turn over after a clatter and white smoke, briggs stratton, grass clippings

Question
Hi Ben, I have a JD L108 lawntractor which is about 2 1/2 years old.  It has a Briggs $ Stratton 31 18.5HP engine. Today I was slowly mowing wet, medium length grass when there was a clatter from the engine and white smoke, no particular smell. There was more escaping white smoke when I removed the air filter. Now when I turn the ignition it only clicks and does not even attempt to turn over the cylinder. To my shame, when I checked the oil it was below the "ADD" mark but still registered on the dip stick and when I push the mower in gear the wheels turn so I hope I have not seized the engine. I did change the oil and filters at the beginning of the season (I am in New Zealand so that was six months ago) Can you offer any possible diagnoses for these symptoms.  Much appreciated.

Answer
Martin

White or black smoke may also result from yard debris, oil, or other contaminants on the exterior of the cylinder as the temperature after a few minutes of operation will reach several hundred degrees F even with proper cooling. Stop the engine and let it cool for a few minutes. Then, check around the cylinder, cylinder head, and under the shroud for grass clippings, leaves, oil or other spills, dead rodents, etc. also you valves may need adjusted or the battery may be bad.