I have an electric scooter and would look like to put a small generator on it. I have not found anything of reasonable size and weight so I am looking into the possibility of putting my own together. I have found some electric radio control motors that would work to generate electricity. Now I am looking for a small (35-50cc), lightweight compact 4 stroke engine to connect to the electric motor. Durability is also important. It will be running at virtually a constant speed. Any suggestions?