Now I see that you didn't mention in your question, "Looking into building a 4 stroke rear drive bike that has the proper brakes for safe stops"
A 212 cc mounted on the rack overhanging to the right so the chain lines up is one heavy cumbersome beast......
How much does a 212cc plus clutch weigh?
Be aware that cheap centrifugal clutches jerk and grab with a 212 cc.
I see you are in Socal so I am inviting you out to the Sat Oct 22nd race at Grange Motor Circuit in Apple Valley
Come on out to see the state of the art in motorized bicycles.