Small Engines (Lawn Mowers, etc.): Briggs and Stratton Engine Wont Start, briggs and stratton, mtd riding mower

Question
Have had this MTD riding mower for 9 years and has never started correctly.  New batteries and starter have not helped.  When you try to start, it turn and gets stuck...as it if doesn't have enough juice to crank.  I jump start it with a car and it barely gets it to turn, but then it goes and I cut my grass.  Have been doing this for 9 years.  Quite tired!   I checked the valves, they appear to be operating (not stuck).  Sometimes backfires.  Checked shear pin on flywheel, looks good.  Please help.

Answer
You either need to adjust the valves or replace the cam.  The compression release isn't working. COMMON!  Set the valves at .006 and see if the problem goes away.  I'm guessing it won't. 9 years ago the cam could have been replaced under warranty. I think that ship has sailed.

If you turn the engine backwards until you feel compression and then hit the key it will speed by the tight spot and fire up.