Thanks guys -
Like i said earlier though i've got the material and gears sitting around and i'd like to build a transmission just for the heck of it. At this point, i'm not building this because i want a mini-bike. I've built plenty of go-karts w/ torque converters or just chain drive and they work pretty well, in fact one will hit 45mph on a straight shot. I've built small transmissions for go-karts but they were from small gears used in a self-propelled walk behind mower. They were never designed to take the stress that driving a go-kart at 20+mph put on them. If i wasn't breaking a part i made then i was breaking gears. Now i have some heavy duty ones from an old heavy riding mower. I'd like to do something with those-build a more sophisticated transmission just for fun. I though a mini-bike would be an interesting medium for the new trans since i've never made one before. I really appreciate all of the advice though. I guess i should have made it clear that the main purpose of this mini-bike was to have something that used a new, "sophisticated" homemade transmission. I'll keep thinking and playing around until i settle on something. Hopefully i can post some pictures. It should be a fun project.