I had a similar turn signal issue on my Kingpin. Turned out to have a break in the wire in the harness where the forks met the frame. You may want to trace it back.
If you do this do it with the bars in a few positions. On my Pin the break would correct itself with the bars locked left as it would sit when parked. As soon as they were straightened or turned right they would stop working again. This made me think it was just a bulb as I changed it out as she sat in my garage and they worked. Then when I took her out they weren't again.
13 Vision Tour - PCV, Top Filter, Stage 1 Pipes, TW @ +4, Metz 888s
08 Vision Street Premium - VFC, Top Filter, Stage 1 Level 2 Pipes, E4s
Past Vic - 07 KP Tour - Stage 1, S&S Intake