Mike---If you still have the "jumping speedo", it could be something as
simple as a dry cable. First, disconnect the inner cable at the speedo
and pull it out of its sheath. Apply some kind of grease to it as you
re-insert it into the outer sheath. Be sure there are no tight bends
that this cable has to turn en route to the instrument. Such bends can
also wear out the sheath and a mere greasing will be short lived.
Re-test.
If you suspect the sheath itself is toast, replace it with a new unit.
They're cheap. Grease this one before installing, for added life.
You can test the speedo itself with a short piece of an old cable,
chucked up in a high speed drill motor. If it still bounces, you'll know
what has to be done!
Dick
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