650 custom rear turn signal housing removal replacement how to
It's not complicated, but it took me a minute to finger it out. You gotta remove three nuts from the studs (blue) that are located behind the taillight and into the rear fender's frame structure (green). The red circles are the #3 Phillips screws that you can see to either side of the taillight when everything is installed.
Leave the #3 Phillips screws secured until you remove the 3 nuts. It helps hold the taillight/license plate assembly in place while you wrestle the 3 nuts (10mm deep socket, 1/4" drive ratchet). The nuts are one-time use nylocks. There are flat washers, too, but no lock washers. There's plenty of room to get your hands in there without removing the wheel. Getting the nuts back on took a small amount of patience.
Wire routing is painfully obvious under the fender and the turn signal housing, wires included, will pull out once the turn signal stalk clamp is loose.
Put some Dielectric Grease on the taillight bulb contacts while you have it apart.