I’m going to replace the main wiring harness. This requires removing a number of connections inside the headlight shell, pulling the old harness out of the headlight shell and then installing the new harness and connecting the wires to the proper terminals on the wiring block, the headlight relay and the turn signal relay. You do not have to remove the connections from the left and right handlebar switches to replace the main wiring harness.
Bur, since I am converting this 1983 R100RS into an RT configuration and the RT handlebars are much longer than the RS bars, the stock RS handlebar switch wires are too short; 230 mm (9 inches) vs.the RT switch’s 520 mm (20 inches). However, someone replaced the left handlebar switch with an RT length switch, so that’s fortunate. But the right handlebar switch, that was also replaced at some point, has shorter 380 mm (about 15 inches) wires; they are longer than RS wires, but still too short. Since BMW does not sell the RT switches anymore, I will lengthen the wires in the right handlebar switch cable.
Here is how I did that work.
And here are videos summarizing the procedure.
VIDEO: 1983 BMW R100RS Replace Main Wiring Harness
VIDEO: 1983 BMW R100RS Lengthen Handlebar Switch Wires
Here is the new main wiring harness I got from Euro MotoElectrics. BMW not longer makes this harness.
Here is the final product.
thank you very much for the effort in putting this great resource together, it helped me reverse engineer the previous owners electrical modification and switch back to standard wiring. `i’m sure this will not be the last time I’ll visit the site having a 1983 r100rs.
There’s nothing so frustrating as disentangling a rat’s nest of wires that someone kludged together. I found a couple of wires on the wrong terminals in this bike’s headlight shell as well. I;m glad to hear you are keeping another ’83 RS on the road.
Hi Brook, me again. I got all my wiring harnesses from EME, I think you did as well? My question is about the headlight-shell grommet for the main harness. The grommet is much larger than the hole in the headlight bucket. Did you have the same issue? There’s no way it will fit. I’m thinking about looking for a new aftermarket grommet, but I will have to split it and place it around the harness because I’ve already got everything wired up in the shell and it was such an ordeal that I really don’t want to disconnect everything now.
I think I had to replace the grommet once and did it as you suggest: split the grommet and install it in the hole. Then I put a dab of silicone seal on the cut line to ensure it was water tight. You can put the dab on the cut line inside the headlight shell if you don’t want it to show from the outside.