Horn and signals do not work on your 1981 Yamaha xs1100 midnight special?

Answer 1

Let's begin with an assumption that the bike starts and runs, and the headlight and brake lights work. Check fuses first, then check the electrical connections on the horns for corrosion and get them clean. If the horn still doesn't work find the screw and locknut on the horn, release the locknut and carefully turn the screw 1/2 turn in one direction, test, then back to initial position and 1/2 turn in the opposite direction and test again. If it starts to sound, tune for power and re-set the locknut. I have returned many horns to operational doing this.

Remove and check turn signal bulbs for continuity to be sure they are good. Replace bad ones with the specific stock type bulbs - others that will fit may draw more current and slow or stop the turn signal flasher. At idle, flashers may cease until revs rise.

Other items that may impact performance are corroded contacts in the switches or a poorly performing charging system.