The Stovebolt Site Forums The Shop Area Interiors [Solved/Updated] Speedometer Re-Assembly....

hi NorthCoast3800
the thing you refer to as a clutch is actually a magnet in a metal enclosure, there should be zero contact between that magnet (the part you broke) and the drum enclosure
the magnet spins and induces a current into the drum that causes it to get dragged with the rotating magnetic field

any disturbance of the clock spring will result in the speedometer being off, the clock spring is calibrated to read true on the dial when the drum is being dragged by that magnet, it's K value sets the angular displacement of the needle and as the clock spring wears (rusts and ages) the speedo will error on displaying a speed faster than what you are actually going
but this time increasing error will be more than overcome by the magnet losing it's magnetism which results in the speedo displaying a value slower than what you are actually going

the clock spring is very delicate, if you massaged it too much cleaning it then it might be no good already, but can't hurt to fix it all up and test it

the magnet can be re-magnetized so that the speedometer is true to correct reading again assuming all the other bits are clean and lubricated just where they need to be
do not get oil on the clock spring
spinning the input of the speedometer in the direction of needle deflection at 1000 rpm should result in a reading of 60 mph

there are other posts in this forum about speedos and how to set up the magnets and make it work again, i have fixed a couple of them to date, they are delicate but not impossible to fix
i bet i could even fix the broken magnet one if you have most of the pieces, the magnetic field would not care if the bits were crazy glued back together then re-magnetized in unison.
best of luck
-s