Andy: I like the idea, but wonder about balance. It looks like you
will have to stand on the engine in order to hold it on the ground.
(your rawing is tiny on my screen). If you stand too far forward,
steering is apt to be difficult, isn't it? You will need rear brakes.
If you rely on just the front brakes, you'll stand it on it's nose. Is
it chain drive? The word above is "drawing", by the way. Great
project! Tell us more.