I'm honestly not sure how people do it, but I know you can use the pedal crank as a function pedal and a jack shaft. I think Pat sells the crank mechanism for it. Maybe message him?
Rocket, that’s the part.....
Very few people have run engine power THROUGH the bottom bracket (BB) and kept functional.pedals.
I haven’t seen it happen on these forums in 15 years.
It seems easy to do, but it’s not.
Engineering problems occur, as you know.
Even if you were to perfectly align the engine sprocket and chain ring, you wouldn’t have a low enough gear ratio to power the engine decently through the bike’s gears.
And if you don’t use a jack shaft to align your clutch and chain rings, your engine sticks out too much on the right side.
A 2-stroke engine might need 35:1 or better gearing before transferring power through the BB.
My 212 engine needs 9:1 gears thru the BB to drive my 7th gear effectively.
Without a jack shaft, I’d need a 10t clutch with a 90-tooth chain ring sprocket!
So sending power through the BB is one issue.
Gearing it to high potential is key.
You’ll hear people say “It runs so-so, but it runs powerless in the last 3 gears.”
Orrr “The engine won’t kick in, until I’m pedaling 15mph!”
I’ve only seen one example of running engine power thru the BB with functional pedals on YouTube.
Oddly, the owner never displayed or explained how his setup worked.
I questioned him in his comments section; he didn’t respond.