What year is the bike, and what year is the harness? From what I can see of the wire colors, I'm making an educated guess that it goes to the Starter Motor Safety Unit (SMSU), which will not allow the electric starter to operate unless the clutch lever is pulled in, or the trans is in neutral, or both. They were used from '73 to '77 cb750s, and I suspect also on 550 during the same years. If you don't have the SMSU, or the switch in your clutch lever, not much of a problem; it can be jumped to allow proper operation of the starter.
