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Hello,
Please help I have a r75/5 (non fused) with a /6 motor. I cant figure out the wiring as the previous owner ran into health problems half of the way through wiring. My wires appear to be the /5 colors. Also the starter relay doesnt have numbers on it so photos or a clear description of the start relay and the headlight wiring would be much appreciated.

Welcome to the forum Chipsdad.

How about letting us know your general knowledge about things electrical? That way the answers you get might be more helpful to you. For example, do you know generally how to read wiring diagrams, or is a wiring harness, with wires poking out of it, one of the most intimidating things you've seen? Also, do you have a DVM and know how to use it?



Ken

my wiring knowledge does not go past reading a diagram and plugging wires back into the correct terminals. although I do understand circuitry and the function of most parts I need help. The problem here comes from the fact that I cant simply follow a /5 or a /6 drawing. Also none of the drawings I have show in detail the placement of wires to the relay and the headlight. Thank you for the quick reply.

Open the link, then scroll down a little.

http://www.airheads.org/content/view/159/98/

Find this heading.

RELAYS 102: BMW info & specs

What relays do Airheads use?

eg

Starter Relays
12 41 1 350 775 [A] /5 (GN/SW-->15, three RT-->30, BR/SW-->31b, SW-->87, two BL-->D+)

There's more there....and welcome.

chipsdad wrote:my wiring knowledge does not go past reading a diagram and plugging wires back into the correct terminals. although I do understand circuitry and the function of most parts I need help. The problem here comes from the fact that I cant simply follow a /5 or a /6 drawing. Also none of the drawings I have show in detail the placement of wires to the relay and the headlight. Thank you for the quick reply.

I don't have a lot of familiarity with the /5, other than its dissimilarities with the /6 bikes. But I do have a couple thoughts.

First, I gather that the /6 engine is sitting in the bike, but with none of the electricals connected. The /6 engine itself is going to be identical to the /5 from an electrical standpoint. By that I mean that the starter, alternator, and ignition connections will be the same as /5, though the wiring color codes may have changed. I would think of the /6 motor as being a /5 motor that needs to be connected properly to your current /5 wiring. That means things like the fuses the /6 uses will be a non-item for you.

I also gather that your /5 wiring is intact, or nearly intact. Or is it that the bike's wiring has been nearly disconnected and you have lots of wires to figure out where they go?

If I'm on the right track you will be working with a /5 wiring diagram, and won't be terribly concerned with /6 color codes.

My approach would be to approach the engine connection function by function. For example you should be able to trace the 12 volt supply from the battery through the connection at the solenoid under the top cover, where it becomes a red wire (battery hot). The 12 volts on a /5 will have to find it's way to the ignition switch (possibly through the starter relay which only physically connects the two red wires--if it's done on a /5 the same way as /6). From the ignition switch in the on position the wire will likely change color. The 12volts has to find it's way through the kill switch thence to the positive side of your two series wired ignition coils. Also, from the ignition "on" terminal the 12 volts will have to find its way to the starter relay connecter where it activates the starter relay.

There are two other functions I can think of. There will be a black wire originating from the engine's points and going to the negative side of your ignition coils. (When the points open the circuit will be opened which will cause the coil to fire the two plugs) The third function will be the alternator. There will be two wires going between the voltage regulator and the alternator. The last alternator function will be a heavy wire going from the diode board to the battery positive.

Hopefully I've got the above right and hopefully the /5 didn't do things significantly different from the later /6. In any event the functions I mentioned have to be associated with the engine. You'll just have to do some tracing.

Maybe somebody with some specific /5 experience will come along and be able to give you better advice.


Ken

I have read the articles and understand what my start relay does. What my problem is right now is figuring which plug on my relay does what. Coming into the relay I have the double red, Brown/black(to start switch), black( i think goes to diode board), Black ( starter). Starter has extra wire off same post going to diode board. 2 blues going to headlight shell, green (horn), The original setup the PO had fired up starter when i grounded battery. The setup I did after trying to follow rough directions did nothing but make lights work.

Welcome aboard, Chipsdad. I don't have /5 experience, but I have fitted a /5 type headlight with an aftermarket electronic speedo/tach to my /6 (actually its a chinese copy of a russian copy of a /5 headlight). In doing so I altered the wiring a bit. I did draw up a map of the standard /6 wiring associated with the starter circuit, which might be useful in your case, provided your starter relay is the same type. See what you make of this:



You won't have the circuit board in the headlight, but you can see what those wires are doing. The diode in there ensures that the starter will not operate unless the bike is in neutral or the clutch is disengaged. This feature is not essential, so the circuit can be altered and simplified.

Hope it helps. More importantly, I hope it doesn't confuse the issue. If you can't make out the colours and numbers in this image, shoot me an email and I'll send a PDF with better resolution. Also, if you don't have a good /5 wiring diagram let me know and I'll scan the colourful one from the Haynes manual. Good luck.

My biggest problems so far seem to be the starter relay. Mine has no markings on the terminals.

Scroll down the link I sent in the post above.
There are schematics showing /5 and /6 relays. They are colour coded to the terminals. Hopefully that'll help.
Here they are anyway.
A = /5, B = /6

holy hanna montana, I would buy you a case of the cheapest beer available for these drawings. hope they work. My relay has one black post but two black wires. I am assuming I will have an open green post and double up the black wire at the connection. Right??