Coalnation has it nailed most if not all Honda's of that age that have RUBBER mounted handle bars will have a black jumper wire with 2 ring terminals on it that is around 3-4 inches long. ONE end goes to the bottom of the handle bar holder under the nut, the other goes to the gauge mounts. It is there because the rubber isolates the handle bar switches from the rest of the bike and can make it so NONE or some of the electrics either don't work or work when they feel like it. That happens because ground for the bars THEN comes from the clutch cable and will flick in and out as the clutch handle is pulled. It can cause things like the bulbs and flashers to burnout, the bike to cut out, and general mayhem of ghosts that seem to come from no where. All from that silly little wire.
Its the only BLACK ground wire on the bike, probably that way so you notice it and wonder where the hell it came from. ;D Shitty thing is, its not on any of the diagrams or the parts fiches that I have ever seen and I spent many hours looking over them.