Rev counter ceased to function

[gavenarmit]

The rev counter on my 51 Jupiter stopped working. I have never tackled a repair to this. Where do I start?

[Jack]

SA or SC? I know on the SC you can see the back of the rev counter, I suspect on the SA you can.

In short, if you reach the collar holding this in to the back of the rev counter, it should be a knurled fitting, unscrew it. Then start up and see if it turns (do not touch the end of the thing, it might be spinning about when the engine turns over) and if it does see if it increases in speed when you rev the engine, out of gear and in a well ventilated area obviously.

If it doesn't turn, it has either been disconnected at the other end or is broken somewhere inside.

It is possible that the fitting has just fallen out of the back of the dial, this is easily fixed, if it has disconnected at the other end it is easily fixed, if broken then I suspect it will need to be replaced - I can't imagine it being easily fixable.

The other thing if it does turn and speeds up when you rev it is that the gauge may be broken, which is potentially fixable but with the rarity of gauges I'd be inclined to leave this to an expert.

Jack.

[Keith Clements]

Assuming this is a standard Jup the rev counter is driven by the dynamo through a 3-1 gearbox and then a cable to the back of the dial. First disconnect at back of dial. Hopefully cable is finger tight. See if you can turn the inner cable with your fingers. If you can then it is likely the cable is broken. If not start engine and see if cable turns. If not then likely gearbox is not working. Take it off the dynamo and see if it functions . If cable does turn then it is likely the dial so plug in again and see if it now works.

[gavenarmit]

Thanks for the info fellas. I will have a crack this weekend.