did you try driveing it w/ the cable disconnected from the speedo and have the end where you can feel if it actually turns, and smoothly?
if you're convinced it's the speedo, take it out and take a look!
bit of a drag, but do-able - on the bench you can use a drill to try spinning it [a cable end helps to attach the drill] - if it really is hooped, open'er up and clean'er out - you might find it's just gummed up, which happens
be careful w/ the odometer wheels, they're easy to break - if all else fails, maybe someone can send you another to try, or new ones are available
Bill
