K75 won't Start

Discussion in 'Old's Cool' started by NickW1, Feb 8, 2011.

  1. NickW1

    NickW1 Been here awhile

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    Need a little help, my trusty 1992 K75 would not start yesterday, here’s what I have checked.
    · Battery: great shape, cranks the engine like a banshee.
    · Fuel: Filter changed last year, tank nice and clean, good gas.
    · Plugs: four months old gaped properly.
    · Kill switch in correct position.
    SO, I pulled a plug and the plug had fuel on it, though I may have flooded it; however, I grounded the plug against the engine and cranked her over….yep… no spark. Checked engine ground that was good, checked the other plugs and they too would not spark. So that leaves the coils or the ignition control unit. My money’s on the ignition control unit; however, is there something I’m missing, something really simple? Many thanks in advance.
    #1
  2. Dolly Sod

    Dolly Sod Red Clay Halo

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    Does this bike have clutch and sidestand safety switches?
    #2
  3. bmwrench

    bmwrench Long timer

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    If the plugs in a K-Bike are wet with fuel, they often will not spark. Try it again with a fresh plug or a screwdriver in the cap. Use sensible precautions.

    What was the ambient temperature?
    #3
  4. Zagando

    Zagando BMW uber alles!

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    Boon Boon read my mind........had the same problem one time...
    #4
  5. Paul Mihalka

    Paul Mihalka Old Fart

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    When it gets close to freezing, the K75 will flood at starting. If you have a fully charged battery, you can try this: Hold the throttle almost full. While holding the throttle, with your left hand push and hold the starter button. While cranking slowly close the throttle. If it starts firing, hold the throttle there and keep on running the starter until the engines runs clean. Unless it is super flooded, this will work. Next time for starting in cold weather hold the throttle a bit open while you crank.
    #5
  6. blaine.hale

    blaine.hale Long timer

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    You can't even turn the starter over with either of those going on, so that's not the issue.
    #6
  7. NickW1

    NickW1 Been here awhile

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    Yes, the bike does have clutch and side stand safety switches; also, although my bike is in the garage it was very cold. I work long hours so I will try Paul Mihalka starting method asap. Dirty or broken switches??? Many thanks guys.
    #7
  8. El Hombre

    El Hombre Banned

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    This is why Airheads, points ignition and carbs are so popular. You can actually fix the MFer.
    #8
  9. NickW1

    NickW1 Been here awhile

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    Thanks El Hombre, that helps miles:huh

    Well, grounded a new plug and no spark at the plugs, any ideas other than the ignition module? :cry

    Thanks.
    #9
  10. fastblast

    fastblast iron butt'r

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    i had a similar problem on a '95 k75. turned out to be a loose coil wire. :wink:
    #10
  11. NickW1

    NickW1 Been here awhile

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    Checked the coils with my meter, they read correctly according to my manual; however, the plug wires show no continuity; how is this possible? All three wires show an open circuit, the wires should read 1 ohm max. What gives?<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:eek:ffice:eek:ffice" /><o:p></o:p>
    #11
  12. Dolly Sod

    Dolly Sod Red Clay Halo

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    A small open circuit in the wires can usually be easily jumped by those 10,000+ volts coming from your coils, but not so much by the 9volt from your meter.

    ...but since you have no spark, maybe your wires are shot.
    #12
  13. WeazyBuddha

    WeazyBuddha Carbon-Based Humanoid

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    I'm not a guru in the mechanical arts but I once had a K100RT that would not start, intermittently. Turned out to be the ignition/key switch--just needed a cleaning.
    #13
  14. Uncle Pollo

    Uncle Pollo Long timer

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    i can push start mine ... but i need to move to a hill

    Check your ignition switch it might be dirty.
    #14
  15. NickW1

    NickW1 Been here awhile

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    Well I broke everything down, disconnected everything from the plugs to the ignition module, switch, battery, load shedding relay, you name it it came apart and was cleaned and put back together. I did not notice anything that was dirty or loose; however, after I put it all back together she fired-up on the first try and ran like she was new, I don't understand it but I'm not going to look a gift horse in the mouth, thanks for all the help.
    #15
  16. wirewrkr

    wirewrkr the thread-killer

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    Did you ever upgrade the battery negative cable?
    There was a factory upgrade to MUCH heavier normal sized cable.
    #16
  17. drk40

    drk40 n00b

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    it might also be the brushes in the starter getting too short. in the K-series they're part of the electrical circuit and if they're getting too short they act like a circuit breaker. if it happens again any time soon, put the bike in second gear, give it a good push forward and try to start again. if that tricks works, it's the brushes and you'll soon see some other gremlins showing up with the headlight etc.. happened to my K75 and was a trick I learned on the flyingbrick forum few years ago.
    rgrds
    drk
    #17
  18. bmwloco

    bmwloco Long timer

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    Back in the day, when I sold K75's new, I knew this: the worst thing you could do was show customers how easy they were to start. Do it once or twice, you can foul the plugs pronto.

    Dry everything out, try again, vroom. Not much will kill a K75... much like an airhead, but simpler in a lot of ways (I look forward to the drubbing for this...)
    #18
  19. batoutoflahonda

    batoutoflahonda Long timer

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    I had brush issues too. I got it going by taking the starter apart and cleaning the carbon off where the brushes ride. I actually found the problem after I just bumped the starter looking for the problem.
    #19
  20. NickW1

    NickW1 Been here awhile

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    No, but the current battery ground cable seems robust enough; I did remove and clean the ends though.


    Thanks for the tip, I will add this to my fall maintenance list.

    Brother you aren’t kidding, I learned that early on and that throttle advance is worthless when starting the beast. On a side note what I like best about this Bike is the smoothness, hands down the smoothest bike I have ever ridden and I’ve been riding bikes since 1978, the only thing I don’t like is the lack of power; which begs the question, are the K100’s just as smooth as the three bangers?
    #20