Small Engines (Lawn Mowers, etc.): Briggs & Stratton : 31C707-0154-E1 wont run, briggs stratton, briggs and stratton

Question
pulling flywheel on Briggs & Stratton : 31C707-0154-E1 is there a keyway have gas and spark but no fire the last time i turned the mower off there was a loud backfire now doesn't run....i think that maybe the timing is off.

Answer
yes my friend there is a shear key between the flywheel and crankshaft. BUT, this sounds to me to be a bad coil. A sheared key won't make you lose your spark. It will just throw your timing between your spark, and the compression stroke off, you'll get a spark just at the wrong time to fire the fuel at the right time. The backfire came for the coil faltering before going bad. It stopped it's spark and then fired again before quiting all together. Same thing if you zipping down the highway and turn your key off in your car, and turn it back on again. The cylinder loads with fuel and then wham spark returns to fire the over abundance of fuel in the cylinder. I just changed one yesterday for the very same reason, and symptoms you experienced. Only thing I would do first to be safe, is remove the small wire on the coil first, and recheck for spark. This is your safety cut-off, when a safety trips it grounds the spark at this place to kill the engine. Once disconnected all your safeties are now bypassed. If the spark then returns, your problem is in a safety switch. (seat safety, reverse safety..ect..) I bet it's the coil though if your out of gear, and blades are off, and there is seat pressure.  795315 is the Briggs and Stratton part number for your engines ignition coil. If and when you replace it use a business card between the coil and magnet end of the flywheel for the correct gap..........Tom
I miss understood, was the problem, when you stated "NO FIRE"
Do you also understand you can have spark but not one unable to fire correctly, (weak spark).......You didn't mention the blades coming in contact with any thing to have caused the key to shear which is the reason they do. I have yet to have seen one shear in 20 years without hitting something. I would hope you'd rethink your rating. And ask it to be changed, And if you re-read my answer it should still have been helpful because it did state if the key was sheared you'd have a mis correctly timed spark causing a no start condition.....Tom