intermittent tachometer issue

[the_kirkwood]

Tachometer is bouncing erratically at idle.  When riding it normally drops to zero rpm with some random twitching from time to time.

Is this likely to be a bad tachometer, bad signal to tachometer or maybe a bad ground?

Is it common for these tachometers to go bad?

thanks in advance

[FJmonkey]

The ground connection is almost always the issue.

[the_kirkwood]

Right on.  Thanks

[Pat Conlon]

Also to check is the grey signal wire coming off your right side #2/3 coil. Clean that connection.