Now that I have an account I can discuss some basics of engines, transmissions and so on. In short a technical discussion:

Where to begin? As with any engineering problem we begin with what the limitations are for our project:

1) A combustion engine with a maximum fluid capacity of 50cc (cubic centimeters) to avoid hurdles with VDOT/DCVA/MVA.

2) The ability to operate on biodiesel (typically used vegetable oils passed through a strainer to remove the larger carbon chains)

3) Optional electric start

4) Inexpensive. Both engine and frame must be easy to come by