I got an old Schwinn bike and fixed it up, but the gear shifter doesn't work. My bike is now stuck in a high gear and takes a lot of oomph to get it rolling down the street, so I was wondering if it would be possible to change the speed of the bike without the gear shifter itself? I would like for it to stay at a happy medium speed constantly, without the use of the shifter itself. If you guys have any advice please share.