Small Engines (Lawn Mowers, etc.): riding mower cranks but does not start, engine cranks, safety switches

Question
I have a Western Auto riding mower with 12HP B&S engine. It was running fine the last time I used it but now it won't start. Engine cranks, it is getting fuel (can smell it in exhaust and the plug is wet with gas), but no start. I am pretty sure it is not getting a spark. I held the end of the plug against the engine to ground it while cranking and can't see a spark.

What to check? Why would it run fine one day and get no spark the next?

Thanks for your help,

Terry  

Answer
If the plug is coming out wet, you have no spark.  The most common reason for a sudden no-spark condition is a safety switch gone bad.  Locate the shut-off terminal post on the engine (it should have 2-3 wires connected to it).  Disconnect all of the wires and re-check for spark.  If you still have no spark, the issue is either the plug is bad or the ignition module has failed.  It should be able to jump a 1/8" gap to ground.  If it has spark, you will need to bypass safety switches, one by one, until you find the faulty one....then replace it.  Hope this helps.