Small Engines (Lawn Mowers, etc.): Running Problem, couple mins, carburator


Question
I have a Craftsman mower, model 917.273752, 18.0 HP, B & S engine, approx 4 yrs old, that has been running fine until recently, after 15-20 min of running time, it quits on me, sometimes abruptly, other times sluggish almost like it is running out of fuel and then quits.  I have replaced the air filter, fuel filter, and had the carburator cleaned and it still does the same thing.  After it quits, I take off plug wire, put in a spare plug, place on metal and when I turn the ignition, it sometimes sparks, sometimes doesn't; also after quitting, it sometimes start right up, runs a couple mins then quits again, other times, turns over but does not start...  Very frustrating.  Could it be a coil problem?  Or something else?  I appreciate any advice.  Thank you.

Answer
Ruth,

   Have you tried changing that old plug out and having the condenser and points replaced with new gapping adjustments I bet  if you had that done it would run like the day you got it have your local shop do that and i promise it will run like a new mower.
4 years is about the duration of duty on the condenser and points gapping