Re: So many problems, Just wanna know....?
I'm surprised no one else has mentioned your idea of using a full suspension bike. There will be an issue of engine drive chain tension with this frame. As the rear wheel moves there will be constant tightening and loosening of the chain. If you're a fabricator you might get away with a spring tensioner of some design but It had better work right or you could find yourself with chain wrap and the associated problems it will create. The rack mount 4 stroke engines make using a full suspension frame possible however. You might explore that option as opposed to the in-frame concept. As for welding on the engine...DON"T EVEN TRY. Unless you have access to a couple of old engines of the same material to practice on I can guarantee you'll destroy your motor. That from a guy who has been welding on standard as well as exotic metals for over 40 years.
Age and Treachery Will Always Triumph
Over Youth and Skill & "Charlie Don't Ride"