 controller and throttle
somewhere out in my shop I have a 24volt controller and throttle. If someone whats to build an ebike it will work great. I didn't really find that the controller added anything significant but to have a variable speed throttle was nice I have to admit.
I think the two of them together cost me over fifty bucks. I will be happy to get thirty and I'll ship it for five more. Make the $35 bucks and it's yours. I'll also guarantee that it works.
If you want a scooter engine to go with it, I have a 350watt that probably even has a friction wheel with it. I'm not sure about the wheel at the moment. If you want I can check on it. Send me a pm. | 
