I had a very similar issue a few years back. My tach was all over the place. Finally the front (if i remember correctly) cylinder quit during a ride in the rain. I spent a month tracking the problem down to a ground in the wiring harness lead to the coil for that cylinder. The tach also runs off this coil hence the weird needle bounce. Instead of tracing out the issue in the wiring harness. I ran a separate lead and spliced it in from that coil to the igniter. One other peculiar electrical issue (before the coil) I had was when I turned the handle bars to the right with the bike running, so I could hop off to open my garage the bike would shut off. It always restarted. The issue hear was the wiring harness connection was loose at the junction point under the gas tank. When I turned the handle bars it would pull slightly on the harness and cause an open at the connector. I cleaned the connector up and made sure it snapped together securely and all is well again.
Last edited by groundzero879; 08-09-2019 at 04:04 PM.