In case the OP is not aware, there is no mechanical connection between the cable driven parts of the speedo and the indicator needle. The connection is magnetic. So, unless the indicator needle post is broken, the likely culprit is dried grease preventing the magnetic pull from rotating the needle shaft. The connection is hard to explain, but sort of a magnetized cup in a larger cup. Offsetting magnets...allows for dampening out the fluctuations, etc.
The speedos are easy to disassemble and clean.
