My tachometer bounces around... it only works sometimes lol. Anyone know how to fix this?

 

The solder points behind the cluster need to be worked on to make the connections fully functional, right now your solder points are probably weak. Need to take off the whole cluster out to see the solder points. It's probably on its way out and eventually will stop working, check any wiring too.

 

Also solder the solder joints near the mounting screws on b the speedo. These like to cause problems, same as the tach. Just touch them with a soldering iron till the existing solder melts.

This would be a good time to replace the instrument panew light bulbs as well.

 

If your odometer is still working then I would solder the solder point's again. If yours is like mine and not working then I would swap out the cluster with a different one