Hey all, here is a good place to start on parts when moving to correct materials and the high tech adventure of adding an engine to a bicycle.
Snowmobile Parts, ATV Parts, Go Kart Parts, Mini Bike Part, Lawn Mower Parts, Chainsaw Part and Small Engine Parts
This is a go-kart and mini-bike supply shop. Well worth the time to visit and do it up right. 8-)
Here is a break down list of parts for a mini bike set up. It has all the parts and pieces to correctly set up a drive line.
Mini-Bike (List of Parts)
This next one is a break down list for a go kart build, which should have a great display on how to set up your trike drive and braking system.
Go-Kart (List of Parts)
Good luck and I do hope this will get you in the right direction.