If [MENTION=88907]mconlonx[/MENTION] is on the right track as far as what you want (which seems to be the case to me), but you can't quite figure out how to implement what he is saying, I would suggest that you go visit the closest elderly farmer/trucker/mechanic to help you figure out how to get the bike to stay in a gear you can live with using some combination of existing parts, duct tape, baling wire, and chewing gum. If you live near MacGyver, or the A-Team, they could help too.