I brought home a Huskee lawn tractor with a Briggs 14.5 hp I/C engine. The previous owner claimed to have been pushing snow the last time we had a storm. He said he rammed into something that caused the flywheel key to shear. He had started to fix it and decided to bail on the project. I took it apart the rest of the way. The keyways on the shaft and in the flywheel both look ok. However the bolt (special)that holds the flywheel on, has threads that are less than perfect and they will not engage with the internal threads in the crankshaft. I am planning to clean up the bolt threads with a hacksaw and a file. It appears that the threads are larger than 1/2" and are a fine series. Does anyone know what thread this might be? Any ideas on how to clean up the internal threads? I could probably find out which threads are used and find a tap, but am concerned about making the situation worse. Any advise will be appreciated.