Dead/dying tach?

I have the stock instrument cluster on my 1983 XJ750 Maxim. All the lights work fine, just that the tach doesn't work. The needle will sometimes go up and stick at a certain RPM and just stay there. How can I tell if I need a new tach, or it's not getting a signal or ? How compatible are tachs from other bikes?

thanks!

 

You might be suffering with a gummy mechanism. BigFitz produced a "How To" on servicing gauges, you might look it up and try it out. I've tested electronic tachs with a function generator set at 1K and dialed up the voltage until I saw the gauge respond. You can test to see if the meter coil is intact by ohming out the coil (I think it is between the grey and black wire, I'll have to check). You should see a few ohms, anything over say 10 ohms is suspect.

 

Interesting. I don't happen to have a variable frequency function generator but I can test continuity across the meter. I'll have a look for BigFitz guage servicing tutorial as well. Thanks for the info