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Thread: Start issue K75c

  1. #1

    Start issue K75c

    I am having problems with this bike starting, at this juncture I have replaced the starter motor, the handlbar starter unit and the starter relay has also be replaced.
    Some times I will push the starter button and all I will hear is the fuel pump cycling but the motor will not turn over at all. A few days later I will again try to start it and it will fire up and run fine for a week or so and then the problem happens again. Does anyone have any ideas because my Local dealer out here in Vegas is stumped. In advance thanks for any help given on this issue.
    Respectfully, Neil

  2. #2
    Registered User
    Join Date
    Apr 2005
    Location
    Rapid City South Dakota
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    243
    Sounds some what like an internittent that I had with a K100. Some times it started, sometimes there was no crank, some times it would start to crank and quit before it fired up. It never let me down long term. I did most of the same things you did with no improvement.

    A trivial fact The Starter relay grounds thru the Ignition black box. I think that it is to prevent the starter engaging when the engine is running.

    I directly grounded the starter relay and it never missed after that. It is not a solution but a diagnostic trial. I replaced the Ignition box as soon possible.
    Harold In Rapid City, SD
    1985 K100RT Bullit
    1985 K100XX/EML Bemel

  3. #3
    A bozo on the bus deilenberger's Avatar
    Join Date
    Mar 2003
    Location
    Spring Lake NJ, USA
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    8,546
    Neil,

    Before we continue on diagnostics by replacement (the most expensive way to diagnose things..) - a question.

    Are you sure it's the fuel pump you're hearing, and not the starter motor (spinning but not engaging)? Reason I ask that - it sounds like you're describing the usual symptoms of a sprag-clutch failure (the drive clutch from the starter to the engine)..
    Don Eilenberger http://www.eilenberger.net
    Spring Lk Heights NJ NJ Shore BMW Riders
    '12 R1200R - I love this bike!

  4. #4

    K75 Starting issues

    Thanks for your responses and yes I am sure it is the fuel pump cycling because I also had to replace that earlier in the year and am familiar with the noise it makes.
    Respectfully, Neil

  5. #5
    I suspect hhshort is on the right track. You can make a jumper from a ground to the "grounded" starter relay lead-all inside the electrical box. This will eliminate this possibility.

  6. #6
    Registered User
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    Rapid City South Dakota
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    Using"how to trouble shoot your K100" at the top of this forum and going to the bottom of that web page you will find an interactive wiring chart. The wire you need to ground is the Brown Red. I completly disconnected it and ran a wire from the starter relay tab to ground. I ran my bike several thousand miles that way while looking for a used black box. All you really need to do is use a jumper wire with clips and clip from the tab to a good ground and try your starter. Then if that solves your problem I have black box from a 1990 k75. (Blatant sales pitch)
    Harold In Rapid City, SD
    1985 K100RT Bullit
    1985 K100XX/EML Bemel

  7. #7

    thanks

    Thanks for all your ideas I will give it a go and see what happens i do love to ride this bike and let me tell you this is an irritant. Also i am a bit sad at the fact the bike shop here is not of more help. Thats life i guess.
    Respectfully, Neil

  8. #8
    Dale Rudolph
    Join Date
    May 2009
    Location
    Medford, Oregon
    Posts
    579
    Quote Originally Posted by niles1 View Post
    Thanks for all your ideas I will give it a go and see what happens i do love to ride this bike and let me tell you this is an irritant. Also i am a bit sad at the fact the bike shop here is not of more help. Thats life i guess.
    Respectfully, Neil
    Neil; I am not that surprised that your dealer is not of more help. I have a 92
    K75RT. While visiting the Los Angeles area a few months ago, I spent a little
    time looking at the new BMW's at one of the largest dealerships in the U.S. and
    asked about getting a quote on doing a valve adjustment. I was told that they
    couldn't do it as none of their mechanics were trained in bikes more than about
    10 years old. The closest dealership to me here in Oregon, Hansen's BMW in
    Medford, who has been in business since 1972, has mechanics that can work on
    just about any BMW made. See if you can find an independent shop or a dealer
    that has been around for more than 25 years.

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