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Thread: Where to Start When the 90/6 Won't Start

  1. #16
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    [QUOTE=typ181r90;898584]
    Quote Originally Posted by cseltz View Post

    The R90/6 DOES have a clutch switch (at least since the '75 models), but it doesn't need to be present for the bike to run. Mine was broken and disconnected for years before I finally replaced it, just had to start the bike in neutral for those years. There is a neutral switch, but when that goes the neutral light won't come on but it seems like it does for the OP.

    My idea of the problem would be with the starter relay. Take the tank off, check the connections and clean them, sometimes it just takes removing a terminal and putting it back in to get the connectivity back. I once rode 15 minutes to get gas and after filling my tank got the exact same symptoms as you. In that case I overrode the relay and got home, once home all I did was disconnect everything, clean it up, and everything worked fine again
    When you had this experience, were you able to "bump" start the bike? I was curious of it would have run by pushing it in 2nd gear, getting it running and then get home .. or .. was the electric completely shut down so it wouldn't run at all?

    I have used bump starting many times!

    That's why I really regret it when BMW removed the kick starters. I had one on my R90, now missing it on my R100 !!

  2. #17
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    [QUOTE=jimmylee;898635]
    Quote Originally Posted by typ181r90 View Post

    When you had this experience, were you able to "bump" start the bike? I was curious of it would have run by pushing it in 2nd gear, getting it running and then get home .. or .. was the electric completely shut down so it wouldn't run at all?

    I have used bump starting many times!

    That's why I really regret it when BMW removed the kick starters. I had one on my R90, now missing it on my R100 !!
    I never tried to bump start. When the problem with the override switch first came about, the bike was still in my basement. Jiggling the wires made it work. I guess a loose connection. I would have to trace the override switch circuit to see what it interrupts but by doing that, you should be able to figure out if the bike should start w/o the electric starter. I guess since bump starting requires the clutch to be out, it would have to. Right? Otherwise no bike with that switch could be bump started.

  3. #18
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    First thing I would do is use a volt meter.

    1. Check and see if you are getting voltage TO the start button

    2. If Yes, then check to see if you are getting voltage FROM the starting button switch TO the starter relay. Remember, there will be a terminal that will show "hot" when ignition is turned on OR hot all the time. It is the relay that connects this hot voltage to the starter to energize it. (I am assuming a generic (sort of) connection here as particular wiring situations may exist - check your particular wiring diagram.

    3. If yes, then check to see if you hear the "click" of the relay and are getting voltage OUT of the starter relay.

    4. Be sure to also check ALL other "safety" switches that may affect this - like the kill switch, ignition switch, kickstand safeties and clutch safeties.

    Just hopefully helpful, because I certainly am not an expert, and have been bedeviled by these German wiring systems. They seem bazaar to me and quite illogical.

    For example, just recently my son's K100 had an electrical problem which evidenced itself by HUD display lights and headlight flickering. Loose connecting wire, right? Wrong.

    He learned from others on the K-bike forum that the problem was the starter brushes being either dirty or need replacing. He took apart his starter, cleaned the brushes (which didn't need replacing) and commutator and voila! Took about an hour. Everything is again working perfectly! Does that seem logical that the starter brushes needing cleaning would cause the lights to flicker?

  4. #19
    Registered User amiles's Avatar
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    With the battery good as you say, I would disconnect & thoroughly clean the battery terminals & ground then test. Next with the battery disconnected remove the fuel tank & starter cover, using your wiring diagram for guidance clean & lube all the terminals in that area, relays & all, being careful of the likely brittle insulation on the wires. (good to do anyway)

    If still no luck, tracing the wiring from point to point with your voltmeter should lead you to the problem, again the wiring diagram will be key.


    I don't see how the suspect coils would prohibit the starter from cranking.

  5. #20
    Registered User dmftoy1's Avatar
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    If your starter relay is good you'll have power at the two center terminals (heavy red wires). If you only have power on one side it can act like you describe. (Had same problem). You have to use a trouble light though as in my case my voltmeter showed voltage on both, but one side wouldn't light the light.

    Load test the battery too just to be safe.

    Just my .02 and experience with the worlds most expensive R90/6.

  6. #21
    Benchwrenching PGlaves's Avatar
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    Quote Originally Posted by jimmylee View Post
    He learned from others on the K-bike forum that the problem was the starter brushes being either dirty or need replacing. He took apart his starter, cleaned the brushes (which didn't need replacing) and commutator and voila! Took about an hour. Everything is again working perfectly! Does that seem logical that the starter brushes needing cleaning would cause the lights to flicker?
    Yes, beccause the designers wanted the headlight and other loads to go off when the starter was running. So they installed what is in essence a headlight relay called the load shed relay. They grounded the relay coil to the starter brush.

    Thus, +12v applied to the relay coil, grounded at the starter brush energizes the relay and the lights are on. But when the starter button is depressed +12v is applied to the starter. Back at that relay coil it sees +12v on both sides, lacks a ground, and disengages the relay. The lights go off as planned. Release the starter button, the relay coil regains ground and the lights come on.

    If the brush is worn or dirty and making poor contact, the load shed relay loses its good ground even with the starter not energized and the lights might flicker or just fail to come on at all.

    I wrote about this in this month's Benchwrenching in the Owners News.

    It is a simple rather elegant solution actually.
    Paul Glaves - "Big Bend", Texas U.S.A
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  7. #22
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    Quote Originally Posted by PGlaves View Post
    Yes, beccause the designers wanted the headlight and other loads to go off when the starter was running. So they installed what is in essence a headlight relay called the load shed relay. They grounded the relay coil to the starter brush.

    Thus, +12v applied to the relay coil, grounded at the starter brush energizes the relay and the lights are on. But when the starter button is depressed +12v is applied to the starter. Back at that relay coil it sees +12v on both sides, lacks a ground, and disengages the relay. The lights go off as planned. Release the starter button, the relay coil regains ground and the lights come on.

    If the brush is worn or dirty and making poor contact, the load shed relay loses its good ground even with the starter not energized and the lights might flicker or just fail to come on at all.

    I wrote about this in this month's Benchwrenching in the Owners News.

    It is a simple rather elegant solution actually.
    Thanks for the explanation. When the logic is understood, it makes lots more sense. Whether it is "elegant" or not is debatable as the same results (lights off when starter button is depressed) could have been achieved in other ways which could be more easily solved if there were a failure - or better, maybe failure would probably never even occur!

  8. #23
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    Did you check the fuses inside the headlight?

  9. #24
    Registered User txedomoon's Avatar
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    Solution!

    Sorry for the delays in answering... took a bit of time to get down to business after the first week. But the issue has been resolved.
    I did try the combo approach of WD-40 into the ignition switch and let it sit in the sun for an afternoon. Fired right up! By the time
    I got to get on the bike and go (3-hours later) I was back to NOTHING, no clicks, ticks or turns. One more shot of WD-40 and again
    fired right up. Must have been just enough moisture remaning to prevent contact. Lesson learned -- DO NOT PLAY IN THE RAIN.
    Thanks for all the help and suggestions!
    "You either run... or you rust."
    Tom Petty
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    1976 R90/6 - Berchta

  10. #25
    Registered User amiles's Avatar
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    From what you have discovered I suspect that your ignition switch may be on it's last legs. Next time it acts up try wiggling the key around & see if that helps.

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