Small Engines (Lawn Mowers, etc.): B&S Lawnmower, briggs and stratton, hp engine

Question
Hi Michael:

I have a lawn mower powered by a Briggs and Stratton 3.5 HP engine.  It is about three years old.  My son was mowing the lawn today and it was trying to cut out on him.  We have had a ton of rain here in Georgia, so the grass was wet and thick.  One time it cut off and he looked underneath and said it was smoking in the center of the blades.  He restarted it and then it just quit.  We have been unable to get it to restart.
It tries to turnover but will not start.  I have no reason to believe there is water in the gas, I checked the spark plug connection and cleaned it, checked the oil, and cleaned out the filter which seemed to have a lot of gas in it?  
Do you have any suggestions on how to fix?  Thanks!   Mike


Answer
Hi Mike,

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.
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.  

Another possibility if the problem is fuel related: Check the gas cap to make sure it is venting and not causing a vacuum in the tank.  

Let me know how you make out.
Michael