Engine on a: Schwinn Sidewinder

I have a Schwinn Sidewinder in mechanically perfect condition; I have just rebuilt it and replaced all no-working parts, oiled, etc. I want to mount a reasonably powered engine to it and keep the deraler, which probably means 1-4hp as much more would break the deraler.

Here are my requirements:
Must allow shifting.
Must be "DIY"-able
Must be cheap.

And "if possible.."s
Mid-mounted (within the V frame)
From an old lawnmower or weedwhacker


This might not be possible, as I am on a tight budget, but help is appreciated.

Also: if there is a under $40 universal engine "kit" that I am unaware of, I could use it as well.

I have a sidewinder from when I was a youth, I thought about using it for my project bike, but decided against it after I read a post about the sidewinder by another owner that said he could not figure a way around the sprocket and the rear drum.

Good luck with it and be sure and let the rest of us sidewinder owners know how to get around the rear drum issue.

myke