new bars!

[Rich82GS750TZ]

Could be corrosion in the socket. You did you clean up the bulb socket, right? Or It could be that the bulb was 41 years old and just died of old age.

[Grimly]

Favourite killer of bulbs on a lot of bikes is vibration, but the GS's don't suffer from it much.

[Cipher]

my brake light is mounted in a rubber ring.
May be a coincidence or a connection clean up lowered resistance and zapped the old filament.