Petrol Mini Motorbike How to Disign the Proper Way, With Honda Gx25cc

Ok this has been a small project that i have done, it is a honda gx 25cc hedge trimmer engine attached to a small push bike, with bigger handle bars and so on. the engine is mounted by a solid metal frame, welded on. then the engine is lined up with the back wheel, unlike the other little drives, with a roller onto the wheel it is driven by a bike chain. There is a shaft extended out of the gear box of the hedge trimmer engine and a welded shaft onto it. it has a small gear held onto that, that is then lined up with a big cog at the bottem to give it a low gear ratio to not strain the engine. it is revved by a old gear shifter off a push bike, much like a quad bike. i also have a kill switch to stop the engine. the engine is 4-stroke so it uses very little fuel, for how fast and far it can go, and you can still peddel if you want to go faster!. i want to make another video on it. but here are some pictures and a video to help :D please tell me what you want and also look at my other youtube videos thanks :D
watch my video here vvvvvvv