So i have never seen this 'bouncing needle' issue with my speedo. A couple weeks ago i moved the speedo cable and then melted it against the exhaust, so i ordered a new one.

The new one was bearmark, so i expected better quality. My original had a plastic nip that went into the back of the speedo, but this one had a continuation of the cable that was square. It was a bit too long, so i trimmed it back a little so it would fit intot he back of the speedo.

The speedo is accurate, but now it jumps and bounces all over the place!

So what causes this bouncing? I s the plastic nip type better than the 'direct feed' off the cable?

Needle bounce can be caused by a number of things, such as a bend or two being a bit too tight instead of a long flow, the input to the speedo might not be fully seated, the speedo might be duff, and so on.
Check the easy bits first, and make sure that the square drive sits home in the transfer box, and that the clippy-in plastic fitting is fully home in the back of the speedo.
It6 shouldn't matter if the speedo shaft is plastic or squared off at the end.

I replaced my speedo cable following failure and I still have slow speed needle bounce. I think I read you need to soak the whole thing in some thin oil to get it fully lubed. Problem is it's a PITA job so I'm sticking with the bounce.

doriz said:

I replaced my speedo cable following failure and I still have slow speed needle bounce. I think I read you need to soak the whole thing in some thin oil to get it fully lubed. Problem is it's a PITA job so I'm sticking with the bounce.

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If it isn't a new fangled teflon lined cable, there is a fairly easy way to do it. Unscrew the top end of the cable from the speedo, cut the corner off a plastic bag, and put it over the cable, and tie it tightly with binder string around the cable outer. Then pour the thin oil into the bag, and hang it up and leave for a day or two while it runs down the cable.