Make sure flywheel key has not sheared. Remove blower housing, flywheel nut and anything else in your way so you can look down from the top of the engine and look at the crankshaft/flywheel key. If it has even a hint of being out of alignment (shear) it needs to be replaced. The best way is to remove the flywheel for inspection but this takes a few special tools and I don't know your level of ability or the tools you own.