gauges bouncing around

[1977GS550]

On long rides, the gauges on my (1977 gs550) speedometer and tachometer start to bounce around instead of staying steady. Another major problem that I noticed today was that in addition to doing this, my speedometer didn't want to go above 50, until it was obvious that I was going much faster. What could be causing this? Like I said, it's only on rides that are around 25-30 miles. It actually did it to me once on a very short distance ride on the freeway. Do I need new cables or more? Thanks for your time

[oldrookie]

Do a quick search for the issue of a slow tach and you will find a lot of information about how to lube the cables. There are several threads on how to get into the gauge housings and clean/lube them.

Mine starting funky things too, but mine are easier to get into than the GS bikes.

[Souske]

Try lubing em up