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Thread: '88 K75C won't start and stranded me

  1. #1
    Registered User K75solo's Avatar
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    '88 K75C won't start and stranded me

    Well, on my ride to a sports bar to watch Nebraska get pummeled again a few weeks ago, the 1988 K75C sputtered and died and I coasted over to the side of the road, seeing it as a portent for how NU would perform. After several minutes I started it and arrived at the bar in time to see NU pummeled. Upon leaving, she wouldn't start and I ran the battery down quite far. Turned over but wouldn't fire. I had a buddy bring his truck out and hauled it back into the garage, where it sits. I haven't looked at it since. It has 174K original miles and I just don't want to put much money into it as it isn't worth much. I got a lot of comments at the BMW rally in SLC though as I just didn't see many C models and none as original or in white as this one. Anyway, scouring for information leads me to Hall Effect Sensor. Of course I want to start simple first and want to look at the fuses. I changed fuel filter two years ago and maintain it mostly myself, though I am no mechanic. The local BMW mechanic was not very enthused about putting time into such an old bike, and I understand. My first check will be the the fuses. What should my second, third, and forth checks be? If it is a Hall sensor, that would probably not be worth repairing. If I can't cheaply repair it, I may just keep it as an objet de arte.

    Thank you.

    Image of the long trip home:
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  2. #2
    Step 1 - make sure the fuel pump is coming on. Key and kill switch "on" just stab the starter button - not really cranking - and listen to see if the fuel pump starts and runs for a few seconds. Open the filler cap if necessary to hear things.

    Step 2 - check for spark. Remove a spark plug. Use a jumper wire to ground the threads of the plug. Crank and observe that the spark plug sparks, or fails to spark.

    Report back.
    Paul Glaves - "Big Bend", Texas U.S.A
    "The greatest challenge to any thinker is stating the problem in a way that will allow a solution." - Bertrand Russell
    http://web.bigbend.net/~glaves/

  3. #3
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    Probably/usually simple or not that expensive to repair the trouble. When it is your machine, one always goes for the worst scenario. Kinda like my wife goes straight for "death" in any risk taking beyond "staying at home with the cat". I understand the difference between it happening to you and happening to someone else. Been there plenty of times.

    The K75's are too nice a ride to relegate to the Stationary Two Wheeled Club.

    There are people on this forum who are willing to help you through any troubles. Just listen and heed their advice. The advice is as good as gold considering those people are not able to get anywhere near your bike physically. Methodically try one thing at a time. You'll get it.

    I've got a few/some spare parts and will lend them as needed for trouble shooting. Just PM me if needed.
    I never check them (pm's) so let me know here if you send something to get it started.

    Charlie

  4. #4
    Registered User K75solo's Avatar
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    Appreciate the encouragement! I will start troubleshooting it when time permits and will keep you and the others posted on my findings. Nice to know others are so helpful and passionate about these machines.

  5. #5
    Registered User K75solo's Avatar
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    Check back... good news!

    So I tested the fuel pump as recommended and I'm checking back. No sound of the pump energizing so I thought I would check fuses to see if anything was the matter and a 15 amp fuse was blown. I replaced the fuse and listened for the pump and heard it! After a lot of cranking the cantankerous engine fired and smoked a little and I test rode it and restarted it several times. Is that it! It lives! Thanks for you guys encouraging me to not give up so quickly, but in my experience in this hard life, rarely do things resolve quite so easily. This buoys my spirits. So, I am going to have the rear tire changed, change the filter and oil, stabil a little gas, hook up a battery tender, and have it ready for the spring after a bitter Idaho winter. Picture of the fuse and a couple pictures next to my rental unit. The leaves are raining. Thank you.
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  6. #6
    Fortis Fortuna Adiuvat Omega Man's Avatar
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    Nice that you got it running.
    The fuse went bad for a reason. I would check the circuit diagram and confirm what is on the circuit. If it is indeed the fuel pump circuit, and only the fuel pump on the circuit, the pump could have “stalled” or “jammed” causing the fuse to fail. Conditions such of hot or cold can change the amperage draw on the circuit. A 12V amp probe would help in testing but not many have one.
    Keep an eye on it. Good luck.
    OM
    "You can do good or you can do well. Sooner or later they make you choose." MI5
    Mod Squad
    2009 F800GS 1994 TW200

  7. #7
    FUKENGRUVEN SURVIVOR akbeemer's Avatar
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    Quote Originally Posted by K75solo View Post
    So I tested the fuel pump as recommended and I'm checking back. No sound of the pump energizing so I thought I would check fuses to see if anything was the matter and a 15 amp fuse was blown. I replaced the fuse and listened for the pump and heard it! After a lot of cranking the cantankerous engine fired and smoked a little and I test rode it and restarted it several times. Is that it! It lives! Thanks for you guys encouraging me to not give up so quickly, but in my experience in this hard life, rarely do things resolve quite so easily. This buoys my spirits. So, I am going to have the rear tire changed, change the filter and oil, stabil a little gas, hook up a battery tender, and have it ready for the spring after a bitter Idaho winter. Picture of the fuse and a couple pictures next to my rental unit. The leaves are raining. Thank you.
    What’s a nice Wyoming motorcycle doing spending the Winter in Idaho? ❄️ ❄️ ❄️
    Kevin Huddy
    Tm Pterodactyl MT Outpost

  8. #8
    Registered User K75solo's Avatar
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    Wanderlust

    I can't stop moving around the country! But I do think that I will settle some day in either Wyoming, Idaho, or Montana. Sort of like this area. Wide open spaces. But riding in the city of Boise is not my idea of a good time. A lot of motorcycle fatalities this summer in the city.

  9. #9

    Thumbs up

    Quote Originally Posted by Omega Man View Post
    Nice that you got it running.
    The fuse went bad for a reason. I would check the circuit diagram and confirm what is on the circuit. If it is indeed the fuel pump circuit, and only the fuel pump on the circuit, the pump could have “stalled” or “jammed” causing the fuse to fail. Conditions such of hot or cold can change the amperage draw on the circuit. A 12V amp probe would help in testing but not many have one.
    Keep an eye on it. Good luck.
    OM
    Dave
    '92 K75S, '08 F800ST, '14 F700GS
    Cedar Falls, IA

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