Join Date: Aug 2008
Location: Whitstable, Kent, UK
weird one - temperamental speedo is a very regular K problem - but you seem to have a variation, mph works, odo doesn't.
You could pull it all apart and look at the tiny plastic cogs and springs, or get yourself on a limited-mileage insurance policy and love the savings!
plenty of people fit a push-bike speedo or trust sat nav.
BTW and FWIW...those in the know about BMW cars of this period warn against resetting the trip meter in motion. BMW are/were famous for using common parts across various models, so it could be a factor. Or not.