Bouncy tachometer fix?

[Guest]

I've had a couple of tachs on my '82 1100GK &, eventually, they all start to bounce around. The needles start to get erratic at about 3 grand &, then, they get worse. Eventually, they fail.
What's a good method of taking them apart & where do you lube them (with what?) to get them working steady again?

[Buffalo Bill]

Well, there are a few threads on the site about this very subject. Try a word search, select titles only.
The hard part is getting the guages open because they were never meant to be opened, there is a way that is not so destructive.

[LarryJ]

I just "practiced" on the last one that stopped working. It didn't take long, once I got the hang of peeling the little lip over.
I found that one had a loose casting, that made it fail. It's the casting that the cable screws onto & it holds the bearings for the magnet shaft. The casting came loose from the plate it's crimped to & wobbles a lot. So, that gauge is junk.

However, now I can dig into the one on the bike, to clean & relube it.

What's a good lube to use?

I also read that I should get a straight cable, WITHOUT the bend in it near the gauge end, too.

[Buffalo Bill]

All from memory, but I think just a drop of molybdenum on the spot.
Sorry, been like 5 years since I done this and that was a Yamaha.
I was originally thinking the problem was the cable, has that been lubed?
Use a thin oil for that.
My tach cable (1100G) just wore out so I replaced it.
My tach was bouncing quite a bit at high rpm, but not since I replaced the cable.

[Brendan W]

I opened mine but it was the cable winding up causing the problem.

[hampshirehog]

I opened mine but it was the cable winding up causing the problem.

9 times out of 10 it's this. Run the tacho using a drill (in reverse) and a short bit of old cable or something similar if you haven't got a bit. If it runs smoothly there's your answer.

[LarryJ]

Well, I opened up the tachometer & lubed the input bushing. I cleaned & checked everything else. It all looks fine & seems to work smoothly. Closed it up. I pulled the cable, made sure it's well lubed. Rerouted as directly & with as gentle bends as possible.
I went out for a ride, & the tachometer still is erratic & sluggish between 3-5grand, reading about 500rpm low most of the time. It seems to be fine above or below that. The mechanism seems smooth as you turn the needle by hand, with no drag or tight spots.
Anyone have any suggestions?
I'm certain that I'm not the first person to experience this.