Bike is my mostly orginal '74 R90s (early Oct. '73 production).
I replaced the aging wire harness about 10 years ago and since then I've had the problem where if the clutch lever is pulled in (tranny in gear), the neutral light will come on. Therefore, any shift through the gears, has the neutral light coming on, whenever the clutch is disengaged.
Can someone verify where the two wires from the clutch switch plug into on the terminal board in the headlight? I'm suspecting a bad diode on the board, but even if I place a diode in series between the brown wire and brown w/ yellow, I have the same problem.
Evidently BMW wanted to protect the +12v from the neutral light from trickling though to the start circuit 85. Don’t know why.
My bike has been that way for the 20 years I’ve had it with no ill effects. I’m also too lazy to pull the contact board out of the bucket. I have a Katdash board now and it’s well protected.
Clutch switch wires: brown is GND 31. Not sure what color your colored clutch switch wire is, but it goes to 85b
Remember, none of this prevents one from engaging the starter motor while the engine is running. DOH!