Originally Posted by KCvale
I'll bet you could too ;-}
The problem is how close the front and back wheels are, like a 20" bike, only enough in the middle for the pedal cranks and back up to clear the front wheel.
Yup.. I keep looking at that area wishing I had some measurements, but stretching the frame does come to mind here.
One could cut out the down tube and use a KTM or one of it's clones as a stressed member to what would be left of the down tube and rigid mounted at the seat post. The bike would definitely need some type of suspension tho if the engine was used as a structural member of the frame to avoid cracking something expensive... maybe a slightly extended Monarch fork up front and convert the rear to a swing arm with a short travel shock/spring assembly or a polymer shock just enough to soften any road roughness would do...