innacurate tachometer readings

Recently replaced solenoid and cleaned the contacts on the fuse bank. About one hundred fifty miles after this repair the tachometer has become wild, most often reading several thousand rpms too high. What could cause this?

What year, and model of bike? Some tach's are cable operated off the front of the engine, others are electrically operated, with the connections coming off the ignition coil.

Dis-regard my question about year/model of bike. I'd look carefully at the ignition coil connections on the primary(small wire side). I believe your bike is set up to have the tach act like a voltmeter when a button is pushed on the instrument panel.