Speedometer jumping

[gazzol]

Hi guys as the title says my Speedo needle jumps around. I had a quick read on the internet and the concenus seemed to be that I needed to grease my cable. At this point I should say that the cable is not the original and I thought I'd got it from walloth nesch 3 years ago however a quick check of my order history says not, nevertheless I fitted a new one 3 years ago. So......I disconnected the cable at the gearbox and tried to pull the inner through but couldn't so I disconnected the cable from the Speedo and tried to pull it through but still no joy. At this point I thought that as I couldn't remove the inner to apply grease I'd apply some oil into the end of the cable and let it run down. I did this several times with a medium weight oil and then reassembled everything............. disaster, worse than before.
Has anyone had similar issues and apart from the obvious which is to replace it what can be done to fix it? I've had a quick look and they appear to be NLA in right hand drive.

 

[Beaudave]

Hi Preston, your thread is almost 3 years old, and you don't seem to have had any reply. I had a similar problem. I sent it here in France to the specialist Renotech, who fixed it. He told me on the phone that many times the problem comes from the cables, which square ends are too long, which apply some pressure inside the speedo, thus resulting in shaking and a trembling needle.
If that may help...

 

[ScottAndrews]

Most speedos, and I suspect this one is no different, use a magnet that is driven by the cable. The cable spins the magnet, and the magnet drags a metallic cup along with it (sort of like a magnetic brake on an exercise bike, but in reverse). The needle and the cup are also attached to a clock spring which causes the needle to return to zero when the magnet is not spinning. If the bearing of rat needle is dirty or otherwise sticky, then the needle may be non-responsive, or it may jump. This can be caused by dirt and corrosion inthe bearing, but it can also be cause, as @Beaudave notes, but pressure on the needle from the cable. Since the cable is spinning quickly, if it catches the needle in any way, it will cause the needle to jump.

I would think that one solution would be to simply add an o-ring tot he inside of the cable end, so that the cable does not go as far into the speedo. The more extreme solution would be to trim the end of the cable, but that may be difficult, and it may introduce metal particles that could make the situation worse.