Tachometer Fluctuating

[dockedwages1]

im having the same problem. Where is the external regulator to check this?

[bjanakos]

Better late than never....

The voltage regulator is located under the black cover near the ignition module and passive resistor. RPM jumping is a common symptom from faulty alternators.

[Paul]

I had a problem with mine, not so much jumping around as drifting, within a range of about 400-500 RPM of what I was actually turning. Turns out all I had to do was turn the selector switch, located on the back of the tachometer, back and forth between cylinder settings a couple of times and just like that no more problem. I guess the internal contacts must have been tarnished.