Small Engines (Lawn Mowers, etc.): 21 horsepower B&S will not start, air bubbles, safety switches

Question
Hi,
I have a 21 horsepower Briggs%26Stratton rider mower.  After winter storage the mower started and ran for about 2 minutes.  I cannot get it running again.  I changed the fuel filter, fuel lines and spark plugs.  The tank was 1/2 full, I topped it up.  It doesn't seem to be getting fuel.  When I pull the plugs, the seem dry.  I can see that the fuel filter filled with gas, although there are still some air bubbles at the top.  I could see a little wasp in the tank, no idea how it got there.  I'm looking for areas to check next.  I may have a problem with spark as well.  Although it ran for 2 minutes and quit, when I put it plug against the intake for the cylinders, I cannot detect spark. Is this a suitable place to check for spark?
Any guidance would be greatly appreciated.

Regards,


Robin.

Answer
You should be able to see spark using the method you described.  Does the engine turn over/spin?

What brand of mower do you have.  If the engine will spin but you do not see any spark then most likely there is a safety switch preventing the spark.  Typically locations for safety switches are the seat, transmission/neutral, and the blade engagement.

You can try priming the engine by applying a small amount of gasoline directly in the carburetor.  You will have to remove the air filter to do this.  If the engine trys to start then you know the spark is good.  If the engine does not even sound like it wants to start then I'd check the ignition system.

Eric