Fix gears inside 1982 GS1100GL speedo?

[Doldrums]

I've looked on here, but can't find the info I need.

The speedo cable on the bike broke. Replaced and it broke again in 200 miles. Realized it is the gears inside the speedo and they are making noise now.

Is it possible to break into the speedo and lube / repair? Or do I need to get a replacement? How do I get into it?

This bike is 99% original - so I'd like to keep it that way as much as possible.
The cluster looks like this (only in better shape): https://www.ebay.com/itm/145605243537

If I can't repair, any help in best step forwards? If I get one off ebay or something, can I turn the mileage to match?

(I would *not* be against putting in slightly brighter bulbs.)

Thanks!

[Lorenzo]

Sorry I can't help with your question;
could you please measure the exact diameter and n. of splines of arbor of the trip meter to which the reset knob is attached?
Thanks