1991 K 75 LT brake light not working

[xcaret]

I noticed my brake light is no longer working. I checked the bulb, it's good ,so is the fuse. I also removed and checked the rear brake switch, and also the front brake switch, both good. There is power at the fuse too.
Any suggestions will be appreciated.
Thanks, Neil 

[frankenduck]

Is the kill switch on? That cuts power to the brake light.

1) Remove tail light lens and verify that gray-black wire is connected to brake light socket.

2) See if it's a bad BMU by removing the BMU and jumping the brake switch wires to the brake light wire.

Front brake switch; gray-red
Rear brake switch: gray-green
Brake light: gray-black

Then try the brake switches with the ignition and kill switch turned on.

3) With BMU removed, jump 12V to brake light wire to make sure that wire has continuity.

[xcaret]

Thanks for your detailed reply.. After checking the bulb ,fuse, both frt and r brake switches , I finaly checked for power at the brake light socket.. sure enough it had power, but the bulb which was lighting up when connected to my battery charger terminals wouldn't light up in the socket.. My owners manual had a note written in by a previous owner saying it takes an 1157 bulb. But they have dual contacts. The bulb that was in the light had been a 1141. I'd never heard of that, but on further reading my repair manuals I saw the brake light is the same as the signal light bulbs . They are 1156 . I put one into the brake light socket and it lit up .
I measured the 2 different bulbs and they were identical as far as I could see. Anyway I bought 2 , 1156 bulbs and now am happily cruising along with no worries of not having a brake light.     

[Laitch]

Congratulations! Thanks for the update.