KZ1100 Spectre non-working Tach

The tach on my 82 Spectre hasn't worked since I've owned it. I purchased another working tach from a member here but it won't work on my Spectre. Where is it that the tach get's it's signal?
Any help will be appreciated.
Bill

If you bike has a button on the instrument panel, that makes the Tach act like a Voltmeter(some bikes did), see if the wiring goes to one of the ignition coils, as this is usually where the Tach got the signal to trigger it. Maybe Green or Black wires.

Signal is from the black wire on the coil for cylinders 1 and 4..

Thanks Guys.

With two tachs refusing to work I'm going to pull the tank and go looking for a bad connection or a broken wire between the 1/4 coil and the tach.

Bill

You can just ohm out from coil to the tach. But unplug the big wires from the igniter so it's not in the circuit.