Re: Stunt bike build
Not to be a kill joy but;
You may as well spare yourself the grief now and nix this idea. You would be far better off looking for a non-running motorcycle that you can restore.
The 80cc MX engines that are made by Honda, Suzuki, Yamaha, produce nearly 15HP. The first time you nail the throttle in an attempt to do a wheelie; the rear wheel is going to buckle and collapse.
If you attach one of these engines to a bicycle and attempt to do stunts, wheelies...etc. It will not live through the first ride.
If you choose to do it anyway, please keep us posted with photos of your build...I've been wrong before, so if you make it work I would like to see it.