Some of us don't mod to go fast (although that is a nice fringe benefit). Riding 2up with a trailer hp and to are necessary. Got confirmation today that my Jim's 120 has shipped. Hot dog!!!

 

I'd like to go back to the original questions: "What should I be wary of? Certain the rear cylinder, heads and piston will need replacing. Should I be worried about the front cylinder? Anything else?"

His description sounds like "sudden engine stoppage." That requires a complete tear-down. The rear cylinder head needs to be magnifluxed to check for cracks, The rear connecting rod needs to be both magnifluxed and checked for straightness. Because the connecting rod is removed, the connecting rod bearing should be checked for true & evenness of wear. If the bearing is deformed in any way, not only should the connecting rod bearing be replaced, but now I'd want to check the crank bearing for true.

There's quite a bit to check, but there is a a progression to it.

That's my $.02