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Thread: Ignition Wiring for (with?) Dummies - K75

  1. #1
    Registered User Didymus's Avatar
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    Ignition Wiring for (with?) Dummies - '91 K75

    I bought an old K75 from a guy I had just met in a bar in Louisville sight unseen and it doesn't have an ignition switch. Not a keyed one at least, just the the little plastic bit that the wires attach to that's left over after you take everything else away. Sounds fishy, I know, but that's not the point.

    The point is that I ordered a supposedly generic, 4 wire ignition switch to replace it but I don't know how to wire it. I'm not a totally lost cause when it comes to wiring. I just replaced the L side switch with a fairly decent soldering job, and installed an all-in-one LED license plate frame without too much hassle. But this switch kind of has me stumped. The trouble is that it came with no instructions and the wires are not labeled. I'm also trying to go from a 3 position switch to a 2 position switch.

    So my question is, is this even possible? Can I wire this thing up without knowing what's supposed to connect with what? And maybe more importantly, am I going to do any damage by messing around with it? I don't mind going the trail and error route, but I don't want to fry anything and end up causing bigger problems than I had in the first place. Should I hold off until I can get a K75 switch or should I just try the wires in different combinations and see what happens?
    Last edited by Didymus; 02-14-2014 at 04:21 PM. Reason: Added model to thread title

  2. #2
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    http://hrsbstaff.ednet.ns.ca/bvogel/...wont-start.htm This web site is is titled "My k100 won't start", buried in it is an interactive wiring diagram. You probably find your answer there. It Will take a little searching. It is near end. Harold in Kansas
    Harold In Kansas
    1985 K100RT Bullit
    1985 K100XX/EML Bemel

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    http://hrsbstaff.ednet.ns.ca/bvogel/...e_diagrams.htm Here is the direct address. Harold in Kansas
    Harold In Kansas
    1985 K100RT Bullit
    1985 K100XX/EML Bemel

  4. #4
    Registered User Didymus's Avatar
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    Thanks, Harold.

    I actually have the kbike wiring diagrams in the back of my Haynes manual. I'm not great at reading them, but that's not the real problem. The trouble is that even if I know what wire goes to what on the bike, I don't have any way of knowing which wires go to what on the ignition switch. The bike has a red, a green, a grey and a grey/blue wire. The colors on the switch don't quite match, but I tried connecting the red on the switch to the red, the green on the switch to the green, the other solid color to the grey, and the striped to the striped blue/grey. Seemed like a reasonable guess, but it didn't do anything.

    On the upside, when I look at the various wiring diagrams, it looks like all the kbike ignition switches are the same. So I guess I can use any of them, and that improves my chances of finding a decent used one.
    Last edited by Didymus; 02-14-2014 at 02:40 AM.

  5. #5
    IBA #44567 Ken F's Avatar
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    Personally I would think you would be much better off finding a used switch to install rather than trying to cobble one in.

    Ken
    IBA #44567
    "Two things are infinite: the universe and human stupidity; and I'm not sure about the the universe."
    -Albert Eienstein

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    Quote Originally Posted by Ken F View Post
    Personally I would think you would be much better off finding a used switch to install rather than trying to cobble one in.

    Ken
    Agree. Sometimes, I think doing something non-BMW is OK, but not this time. All the electrics are intertwined, and sometimes funny things happen. When it does, it helps to have original stuff like this.

    Call RePsycle near Columbus, OH, or some other place that specializes in used BMW parts, and I am sure you can pick one up at a pretty good price.
    "The difference between death and taxes is that death doesn't change every time congress meets." - Will Rogers

  7. #7
    A bozo on the bus deilenberger's Avatar
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    Hi Didymus,

    Please review: http://www.bmwmoa.org/forum/showthread.php?46057 - I'll add the K75 to the thread title, it might also be useful to know what year (some years had a bit of odd wiring that caused both hi and low beam filaments to light at the same time if the high-beam was turned on, and ALL the headlight wiring is routed through the ignition switch, with NO fuse whatsoever..)

    Welcome to the forums - and look for a used switch. If you haven't cut any wires - and the white plastic part is still intact (and working) - all you need is the cylinder portion.. no big deal to do. Even if you do the entire switch, from memory the connector is under the tank, and not that far into the harness.
    Don Eilenberger http://www.eilenberger.net
    Spring Lk Heights NJ NJ Shore BMW Riders New Sweden BMW Riders
    '07 R1200R (current ride) and some bimmers.. and a Porsche

  8. #8
    Registered User Didymus's Avatar
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    Thanks. It's a '91 K75, and I'd like to put that in my signature line, but I don't see any place to do that in my profile.

    In the mean time, I found an '85 K100 switch that I'm hoping will work. Fingers crossed...

  9. #9
    Administrator 20774's Avatar
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    Quote Originally Posted by Didymus View Post
    Thanks. It's a '91 K75, and I'd like to put that in my signature line, but I don't see any place to do that in my profile.
    Click on the link Settings in the upper right of the screen. Then click on Edit Signature on the left side of the screen. You can then enter what you want for a signature. There are some limitations...maybe number of lines, number of characters...but it should be enough to work with.

    Any problems, just let me know.
    Kurt -- Forum Administrator ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  10. #10
    Registered User Didymus's Avatar
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    Cool. Found the spot for changing the avatar too. Added a signature. This post will test whether or not it took...

    Edit: Worked! Thanks.
    '91 K75

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