Inside the left leaver fulcrum, there is a micro switch. I've had mine fail before. Mother Honda still has them (at least they did 2 years ago) and are easy to replace.
To test the switch, trace the wires from the leaver to the headlight bucket. Disconnect the wires. Put an ohm/continuity tester on the two wires from the switch. When the lever is pulled in, the tester should change from open to closed (or closed to open).