14.5 HP Briggs backfiring/won't start after fly wheel replacement

The first time I tried to start the tractor and it failed, I tore it down and removed the new flywheel, and as you said, the pin was sheared. I replaced it and put it back together. Still did the same thing. Maybe it is sheared again. I don't have a torque wrench to tighten the flywheel bolt, so maybe I didn't have it tight enough. Tomorrow I will tear it down again to see if the pin has re-sheared. Thanks for the advise!

When you put the new key in, put the flywheel on first, then slip the key down the slot. This makes sure the flywheel goes ALL the way down on the taper of the crankshaft. Then, TIGHTEN that nut or bolt for the flywheel to the proper torque. It has to be TIGHT, or it'll shear that key again. Most flywheel nuts are about 65-80 foot pounds. The aluminum key is only there for alignment purposes. The taper and pressure from the tight bolt is actually what holds the flywheel in place on the crankshaft. That key is only aluminum, meant to break if something goes wrong with the engine to prevent serious damage.

But the root cause of my problem was the valve clearances were way too wide. So wide that the exhaust valve was not being lifted by the compression release cam. Once I figured that out and adjusted the valves from 30 something thousands to the proper clearance, the engine started right up. The starter just can't spin that big engine without the compression release, so it strips teeth off the ring or pinion. Fish can give you the clearances off the top of his head, I would have to look it up, but it's about 5 thousandths or so. This might be your problem too.

Ichabod