Small Engines (Lawn Mowers, etc.): I have a riding Lawnmower..., riding lawnmower, valve clearances

Question
I have a riding Lawnmower that runs for 30 min. then quits. After it cools down it runs a little while more then quits again. I'm thinking that it might be overheating then it stops running.Any suggestions would really help. Yard machines by MTD..15.5OHV Tecumseh engine. Thanks for your help Jon

Answer
If you have a problem related to heat or time, it can generally be attributed to one of two things.  First you need to make sure you still have spark after it quits.  If you have no spark, the ignition module will need to be replaced.  If you have spark, you will need to listen carefully to engine for a "whisping" sound in the exhaust.  If the valve clearances are insufficient, the valves can hang open when the engine gets hot.  Hope this helps.