Check inside the headlight housing for disconnected/corroded electrical connectors, and then the fuses.
When the bars were replaced, was the original wiring inside or outside the bars?(some bikes are inside).
The rear brake "Bullet Connectors" might be loose/corroded too.Take either a self powered test light or a multimeter and see when the rear brake switch is out of the circuit(disconnected) if it has continuity.
If no continuity, the switch might be bad. Sometimes spraying some contact cleaner up inside the plunger helps clean the contacts so the switch works.
1982 GPZ1100 B2
General Dynamics/Convair 1983-1993
GLCM BGM-109 Tomahawk, AGM-129A Advanced Cruise Missile (ACM)
