Small Engines (Lawn Mowers, etc.): yardman riding lawn mower, fuel flow, compression test

Question
My husband is the maintenence man for our land lord he was mowing the lawn last week and when he would shut the mower off it back fired, then he started mowing again and after awhile it just quit. What could be the problem?

Answer
Hi Jimmy,

You will need to determine if the problem is a lack of spark or a lack of fuel flow.  Right after it quits, remove the spark plug, reconnect the wire and lay it against the engine head.  Pull the engine over and watch for spark at the plug's electrode.

If good, then try to start it while squirting fuel or starting fluid into the carb intake.  If it starts and you can keep it running by adding fuel, then the carb most likely has dirt, debris or gummed fuel inside.
First, check the gas cap to make sure it is venting and not causing a vacuum in the tank.  If that's okay, you will need to remove the carb, disassemble it, clean all the small internal openings and blow it out with compressed air.   Probe each and every hole with a small wire.   A carb rebuild kit wouldn't hurt either.  

The backfiring may indicate a bad valve and require a compression test.

Let me know how you make out.
Michael