Small Engines (Lawn Mowers, etc.): 10 HP Briggs 220707, hp briggs, valve clearance

Question
Won't start has new gas spark backfires when choked

Answer
If the engine backfires on you are trying to start it the first thing to check will be the flywheel key remove the flywheel and be sure the key and the key way are in good condition.  Check the flywheel for cracks.  From there go to valve clearance and valve timing.  If all of those are okay it may be your  ignition coil.  Check these things out and get back to me if it does not resolve your issue