is it possible to change a gear in the transmission(like 1st) to make it a reverse?

 

Why do you want reverse on the bike ??? it's not that heavy

 

putting motor/trans on mini-buggy.

 

No, you can't change a gear and make it into reverse. You'd have to somehow fit an entirely new shaft in the gear case so that it would turn backwards. Check out the schematics for say a TRX450EX or a Yamaha YFM660R (raptor) as they have a reverse gear. Maybe these will give you some ideas.

 

Some one correct me if im wrong. But you have to have a tranny designed to have reverse. A gear change isnt what makes the diff I think. Like I sid if someone knows better then by all means....