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R90/6 electrical question

wbmoore
Posts: 81
Joined: Sun Nov 16, 2008 7:26 pm
Location: Big Bar, Ca.

R90/6 electrical question

Post by wbmoore »

Hey… in the photo below, if you follow the blue circled wire (0.75 sw) to the left where it terminates at “50”……does that mean that it grounds to the headlight shell ? I assume so, but you know what they say about assuming. Thanks.
99B8002D-007F-4330-BAB1-69697D76C724.jpeg
Brad Moore
1960 R69; 1975 Norton MKIII; 1976 R90/6; 1992 K75S; 2000 Hayabusa
Big Bar, Northern California

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srankin
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Re: R90/6 electrical question

Post by srankin »

Taking a quick look at your wiring diagram, the 50 is the spade on the circuit board inside the headlight shell. If you have the proper wire, it will match the color coded area to plug in on the board. LOL, it is a tight fit to get into, at and to see but it makes sense. St.
Owner of a 84, R80RT and 78, R100RS

wbmoore
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Re: R90/6 electrical question

Post by wbmoore »

If I am correct, the “50” on the diagram is Not on the color coded connector board. I have no “50” on my connector board. I have no black space on my connector board.
5B279FC4-CDFE-483E-AA8B-D18EEE7DD64A.jpeg
The harness and the connector board are original to this bike. Thanks.
Brad Moore
1960 R69; 1975 Norton MKIII; 1976 R90/6; 1992 K75S; 2000 Hayabusa
Big Bar, Northern California

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schrader7032
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Re: R90/6 electrical question

Post by schrader7032 »

Look carefully at your diagram. That terminal 50 is not on the board. The board is designated by the circle F and terminal 50 appears to be somewhere else inside the headlight shell. I have the BMW electrical diagrams and it has 3 different versions of the R90/6 diagram. Only two of those diagrams have this "50" on them.

The BMW diagrams have three models listed - 271, 277, 293 for US models for the R90/6. I've never known what that meant. For the R100/7 US models, it lists 333, 314, 393. If I go to RealOEM and type in my VIN, at the bottom of the page it gives the build date for my bike and also that model type 333. So, I guess that helps me figure out which of the three diagrams I should consider for my /7. And there's different type models for European models. FWIW.
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.

wbmoore
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Location: Big Bar, Ca.

Re: R90/6 electrical question

Post by wbmoore »

Kurt, thanks. That told me I’m looking for a #293 diagram. But I’m still wondering what happens at the “50” terminal ??? On the diagram above there are “50” numbers on the horn button, the starter button and the starter motor. Any ideas from anyone. Thanks for any input.
Brad Moore
1960 R69; 1975 Norton MKIII; 1976 R90/6; 1992 K75S; 2000 Hayabusa
Big Bar, Northern California

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srankin
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Re: R90/6 electrical question

Post by srankin »

I looked at what wiring diagrams I have on hand and I concur with Kurt, it depends on the year of you bike. Sorry but yes, on the wiring diagram you have in your picture it looks as if the wire in question goes to the circuit board. I see by the picture of the board you supplied there is no spot for a black wire.

So did you remove the wire or was it just found hanging in the system? Anyway, it is raining today and I am not riding so I will see if I can find something in my diagrams to answer the question.

LOL, this is not the first time I have come across a wire that is not in the diagrams I have, BMW does add wires from time to time in mid year or US versus overseas model changes.

I do believe it may just be for the horn as you said but I want to make sure. St.
Owner of a 84, R80RT and 78, R100RS

wbmoore
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Re: R90/6 electrical question

Post by wbmoore »

St. If you’ll look again, you will see that the “50” terminal in the above photo is clearly not on the outlined “F” “contact plate with fuses”. Still looking for the answer.
Didn’t want this to slip out but….I’m putting a /5 headlight on a /6. I’ve installed the contact plate, the flasher and the light relay in the /5 headlight shell. Everything is almost all hooked up except for the black wire that does to “50”. Thanks
Brad Moore
1960 R69; 1975 Norton MKIII; 1976 R90/6; 1992 K75S; 2000 Hayabusa
Big Bar, Northern California

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srankin
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Re: R90/6 electrical question

Post by srankin »

Well, I am sorry I don't have a direct answer for you. Look at it this way, if you get the changes done you are doing and everything works, did you really need that wire hooked to anything? Is it a live wire? BMW in my experience uses brown wires for ground. Why they did this the way they did is a good question. My experience is there are no grounded black wires in the headlight shell on a R90/6.

I don't have a wiring diagram that answers your question, so I guess I am out of the loop now. Good luck. St.
Owner of a 84, R80RT and 78, R100RS

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Re: R90/6 electrical question

Post by cwf »

I think Snowbum probably has as much if not more info than you want :

https://bmwmotorcycletech.info/wires&codes.htm
75/7+ offroad sidecar; 50/2; R 35; XR125V; XR200A; Solex; 1939 Hillman Minx DHC.

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srankin
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Re: R90/6 electrical question

Post by srankin »

Snowbum shows 50 as starter direct control. This is usually a black wire, and it connects to the starter relay output. Yes, this does come off the relay. Where it goes is the question.

Also,SW black ...usually, not always, the starter, and some functions to the ignition coil, starter, tachometer.

Did you have a mechanical tachometer to start with, I believe this is so? That would rule out a tachometer lead. So, that leaves coil and starter.

Is this wire in the headlight shell or outside on the main harness? If it is in the shell, that makes it a whole new ball game, if it is outside, then perhaps it is a coil wire? St.
Owner of a 84, R80RT and 78, R100RS

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