Tail lights flicker when motor runs

If you find that your BMW 650 CS/GS/Dakar tail light doesn’t work at all or flickers when riding, chances are the metal power terminals inside the bulb socket are no longer making a good connection with the metal bumps on the tail light bulb. This is a very common problem with the BMW 650 of all makes, models, and years. Fortunately, there is a very easy fix.
Due to excessive vibration, temperature changes, and replacing light bulbs, the two metal power terminal tabs inside the tail light socket deform and get pushed too far back inside the tail light chassis. This prevents the tail light bulb from making good contact with the power terminals and the smallest vibrations can cause the electric connection to break temporarily or indefinitely.

To fix the problem, all you need to do is pry the two metal power tabs forward just a little so that they make a better connection with the metal bumps on the tail light bulb. If you look at the back of the bike, the red tail light casing on the 650 CS/GS/Dakar is held in place with two screws. If you remove these screws the red tail light casing comes off and you have access to the light bulb inside. At this point, turn the ignition on, but you don’t need to start the bike. Remove the light bulb by pushing in and twisting clockwise about 1/8 turn. If the bulb flickered while removing it, then the bent power terminals are most likely the cause.
Looking at the tail light bulb you should see two metal bumps. These bumps need to make a good connection with the two metal power terminals inside the tail light casing. Turn the ignition off and find a small tool that you can use to pry the power terminals forward just a bit. Make sure the bike is off and you don’t want the power terminals tabs inside the tail light casing to touch.
After you have made the adjustment, turn the ignition back to “on” and re-insert the taillight bulb. If the bulb is lit, then you are done. If it still flickers a bit and doesn’t stay lit, then you will need to continue prying the tabs forward until a good connection is made.