David - It might be the cable and you can try getting some thin oil to drip down into it. I don't know why BMW made the cable captive, but they did and it makes it difficult to lube. So do whatever you can to remedy.

We tend not to service our gauges until they're ready to blow up - mostly because it's difficult to say when exactly they need it. There's no published service interval that I know of. When I was a kid, the rule of thumb for watches was yearly and our gauges are similar to clocks - sort of. How long the lube lasts depends on use, disuse, temperature, humidity and other factors like damage from water and rust.?

My guess would be that if the gauges haven't been serviced in ten or twenty years, it's probably due. The warning signs that the gauge needs attention is whining or screechy noises, a jerky needle, or erratic behavior. The tach gets a little more of a workout, so it tends to be the first to go.?

For sure, do what you can to lube the cable and see if that fixes, but keep in mind if it doesn't, it's probably the tach meltdown isn't too far distant. I bought a true 14K mile /5 about 17 years ago and rode it home. Within about 500 miles both gauges started screeching, jerking wildly, then melted down. If I had disconnected the cables when they first started complaining, I would have had some like-new gauges once they were serviced. A cleaning and lube would have been enough to get them going again. But since I didn't, wanting the odometer for gas stops, and not bothering to disconnect the tach either, both died horribly deaths and needed rebuilding (rather than just a service) with a lot of new parts.?

Terry? (Wirespokes)?