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Hello gentlemen,
I have a 75 R90S that had a badly damaged LH handlebar switch. Yellow toggle was inoperative,flasher paddle was broken. I replaced it with a switch from a 78 R100. No turn signals as they are on the RH handlebar switch. Wires are easily recognizable and Ive put them on their respective terminals. I have taken an 8 wire switch and replaced it with a 6 wire switch and am having issues. No headlight. Hi beam flasher works,hi beam indicator works. My thoughts were that the headlight would simply be on when the ignition switch was on. But Im not coming up with that yet. Any suggestions. Im still working on it.
Thanks

Yeah, in 1978 the US models were set up with the headlight always on. You need to get inside the headlight shell and rewire the headlight relay so it's energized when the ignition is on.

Per the wiring diagrams in my Haynes, what you need is a black wire from terminal 30 on the starter relay to terminal 85 on the light relay. There may already be a brown wire on 85 at the light relay--remove it.

The black wire may already be in your wiring harness. My 1975 /6 (same harness as your R90S) seems to have it in place, an extra black wire with nowhere to go under the tank. I haven't looked in the headlight bucket to see if the other end of it is there.

Thank you, Yes I see the brn. wire on terminal 85. I will begin to make the terminal 30 to 85 connection.

Thanks again,
There is no power on the terminal at the starter relay. It already has a blk wire on it and the blk wire from the headlight bucket to the starter relay is hanging in the perfect spot to make the connection.
Ill keep poking.

Yes, you may need to piggyback that black wire at the starter relay. But first check to see where it comes out in the headlight bucket. I think there was a spare black wire in the bucket, but I can't say that with 100% confidence.

I may be wrong (I'm away from home for the 'festivities' and don't have access to my reference material) but I think the black wire already on the starter relay is the one that goes to the switchgear and is, therefore, no longer needed. Try disconnecting it and replacing it with the currently unconnected wire. You'll probably have to do a similar thing at the lighting relay. If memory serves, the black wire is the positive feed for the lighting relay coil. On /6 machines (and later Euro machines) it is routed via the light switch whereas in later US spec machines, it goes direct to the relay. If memory is faulty, I apologise in advance...

Rob