Speedo head – is the drive seized? – By forum member Babrat61
If your scooter has been stored and unused for many years , as most out there appear to be, it is worth checking the square internal drive to the speedo is not seized. Fitting a new speedo cable without doing this may result in an immediate failure of the cable inner!
I have accumulated 6 speedos and all were seized!. The internal pinion and worm gear are nylon and are lubricated during manufacture with a white grease. This grease solidifies with age and ‘gums up’ the drive spindle (which the small square section inner of the cable slots into) and the worm and pinion gears.
To unseize the mechanism I recommend converting a small square needle file, by grinding the square down to suit the internal cable size, clamp the needle file in the vice horizontally, slide the speedo head drive spigot onto the modified needle file and the gently rotate the speedo in a clockwise direction. It will be quite stiff at first, but as more rotations are made you will notice a gradual freeing up of the drive and see a deflection of the speedo face needle and after enough revolutions an increase in the odometer. It may be necessary to rotate the speedo up to an indicated 1 mile on the odometer to ensure a super free mechanism.
Some freeing spray may be directed into the square drive of the head, hoping that some leeching of the liquid will occur to help in the freeing up process.
Once you can rotate the needle file freely in your hand and see the speedo needle bounce up to a speed and back again, plus a gradual increase in the odometer reading, it is safe to say that the speedo is functioning satisfactorily.
Under no circumstances try to disassemble the speedo, as the front chrome bezel is crimped on at manufacture and is unlikely to come off without a fight and it certaily won’t go back on again with any degree of satisfaction.