This is a bike which has 49cc engine installed on the rear wheel. The rear wheel is driven by the engine using a friction roller. This makes it possible to manually add power on hills while still using the engine. I made it possible to lift the roller off the wheel, so it is still possible to normally drive the bike (in case of no fuel). There is also a kill switch installed on the steering wheel.
The maximum speed was around 40 km/h and there was plenty of power to drive up a hill.