Faulty Smiths Speedo

I would suspect a break in the cable myself. It might explain the intermittent working if the broken strands are catching every now and then and spinning sufficiently to move the needle before losing contact with each other again. It is certainly worth checking before you start throwing money at it. If the cable checks out ok, you can check the speedo operation initiallyby fitting the end of an old cable in a drill and up into the housing, then spinning it to see if the needle moves.

Try to get a copy of Graham Blighe's book "Magnetis Speedometer Repair". It was a great help to me when repairing my T140 Smiths instruments and most of the principles should read across to other makes.

Regards, Ian

Previously wrote:

If the cable checks out ok, you can check the speedo operation initiallyby fitting the end of an old cable in a drill and up into the housing, then spinning it to see if the needle moves.

A good tip, but you need a drill with reverse function, normal drill rotation is the wrong way & if you spin it too fast you can damage the speedo.

Also check the drive gearbox at the rear wheel, I've had some funny things happen to the speedo needle when the gearbox is about to give up, including very similar symptoms to those you describe.

Hope this helps,

Regards, Tim