I just went through this problem today with my 1980 XS400s. The Flasher which is directly under the rear part of the gas tank (in front of the battery) was only working when the bike was running and vibrating. When the bike wasn´t running (an no vibrations then my right side would just turn on steady but not blink, left still worked okay) Tap it and play around with it. It´s a silver cylinder a little bigger than a film canister. Also, I realized that just by rotating it a little in the rubber sleeve/holder can make all the difference. If that doesn´t fix it, it may need to be replaced. I think it´s possible that Autozone or Checker may even have a generic replacement for just a few bucks. I hope this helps. Good luck.