I show how I route the main wiring harness after I installed the headlight shell. Previously I replaced the main harness with one from Euro MotoElectrics.
Here is the document showing the details and a short video.
VIDEO: 1983 BMW R100RS Routing Main Wiring Harness
Below are a couple of the pictures from the write-up.
Main Harness Cable Exits Bottom Of Headlight Shell
Main Harness Goes Under Lower Triple Clamp (aka Yoke)
Main Harness Goes Between Frame Down Tubes
Main Harness Goes Between Spine Tube and Reinforcing Tube
Front Brake Light Switch Sub-Harness Plug (GREEN–Red, GREEN-Black) & Clutch Switch Sub-Harness Plug (BROWN–Yellow and BROWN )
Main Wiring Harness Coil Power Terminal (GREEN–Blue) Goes On Same Terminal As EME Optical-Electronic Ignition Control Unit Power Wire (RED)