When I first started considering a MB I was only thinking of an electric assist hub motor. I know you can pedal and extend the range of your batteries, and maybe even help it up hills. How does that work with a frame mount gas motor? If your bike is a 21 speed, can you pedal at the same time, or once the engine starts does it just take over? Also, can you shift into different bicycle gear ratios to help the engine make it up hills? Thanks for all info.