Here is an early motorcycle which is an adaption of a bicycle. The motor is below the frame, and the gas tank is attached to the seat tube. The motor grabs the bicycle chain in front of the chainwheel, and takes over from the bike rider. It appears that the pedals would be furiously spinning as the motor drove the bike, so I don't know what the rider did with his feet. Maybe the motor didn't turn the pedals so fast that the rider could not keep his feet on the pedals. There is a throttle on the handlebar.