Re: what are these engines made of?
I had this once. I used a large steel washer that had inner hole that fit the curve of the case where the drive shaft runs thru. I cut a section out of it and ground the outside to match the rest of the motor. I then drill 3 holes in it thru the remaining case, and put 3 bolts thru with nuts on backside & upper left & center bolt heads ground down a bit to clear chain. A spacer just as thick as the broken piece of case to keep it straight when tightened left me with a working motor again that was even stronger than before since the steel part was a bit thicker than the original aluminum part.
Sometimes I sets and thinks, sometimes I jes sets.