Tachometer not working

Hey folks I have an 82 Kawasaki 1100 KZ shaft - my tachometer doesn’t work like it supposed to. I ordered a new one put it on and it does a little better than the older one but not like it’s supposed to. The RPM doesn’t always work sometimes it does sometimes it doesn’t. I noticed there are three wires that control the RPM which wires should I be concerned about and where do these wires lead to?

Brown is ignition live  - test with a voltmeter ( ign on, black meter lead to battery ground - should be with 0.5v of battery voltage)
Black/Yellow is ground - test with a voltmeter (red meter lead to battery positive)
Black is the speed pulse from the "igniter/trigger" ( you can do a "dirty test" with an LED test lamp connected between black wire and battery ground) you will at least see if you have a pulse when the Tacho isn't working