Small Engines (Lawn Mowers, etc.): Briggs 18.5 HP Intek, small engines, exhaust pipe

Question
I have a Craftsman lawnmower that I just purchased from a friend and he said it was "running rough."  It is doing a bit more than that and I am kind of stumped as to where to start.  It will start and run fine for about 5 sec or so and then it starts backfiring through the carb and out the exhaust.  The last time it ran, it sounded like it was smoothing out a bit and I went over to the other side and the exhaust pipe was cherry red.  The guy said he has replaced the fuel line from the carb to the tank as well as the pump and filter.  I cleaned off the magneto contacts as well as the flywheel because I felt like it was a timing issue, but if it was timing, it would not crank at all in my opinion.  The model number is 31P777, the type is 0348, and the code is 040311ZE.  Any help would be greatly appreciated.

Answer
You could very well be in need of a carb rebuild. A engine running lean on fuel will also run very hot. Timing is rarely a issue with small engines. If you removed the coil did you gap it correctly upon install? Gap should be the thickness of a business card.....Tom