I've thought about this for my 3 wheeler build. My solution was to get an electric start version of the motor, which in my case is a 6.5 hp honda clone. These motors come with a charging stator to charge the battery. I'm going to run a small tractor battery, which I'll probably put in the truck bed. When I get my 53 automatic done, I'll jump back on the truck. Check out my 3 wheeler thread for future updates.