My Schwinn Varsity at the Port of Sacramento which confusingly is in West Sacramento where I live. 26" frame. I personally would try oiling the mechanism of the odometer on your bike. Those old odometers were a completely mechanical gears and what not going on in that little box. If it starts getting loud I think oil will quiet it down. When new they just ticked when working. I've had them lock up and it was probably because as kids we never lubed them.