ABS fault-finding, and anyone know what this part is?

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Thread: ABS fault-finding, and anyone know what this part is?

  1. #1
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    Default ABS fault-finding, and anyone know what this part is?

    Hi All!

    New to the site and looking to improve the way I use my F650 GS Dakar (it mostly loses out in competition with my R1200GSA )

    I'm experiencing a problem with the ABS on the front wheel - kicking in every time I brake. I suspect it's a sensor issue. It arose in connection with some maintenance on the forks I had carried out at the BMW dealer.

    I'm not looking to make any repairs myself, but would like to see if I can determine the fault before taking it along to the mechanic.

    Can anyone point me to a fault-finding procedure for ABS on this great site? I've made a determined attempt to search for myself, but with no success. Your help would be much appreciated.

    Also, does anyone know what the cylindrical part highlighted in the attached jpeg does? I've seen it depicted on very few images of the F650, and the manuals I have access to (Haynes for example) don't reference it. Again - help much appreciated!

    Thanks!

    //Derek

    Whats this.JPG

  2. #2
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    02 dakar
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    Pre load adjuster for aftermarket shock ?

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  4. #3
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    Hi Derek,
    welcome to the forum, you not got an easy choice with the R1200GSA in your stable too!

    suggest you check ABS sensor and rota for muck etc, also check wiring for chaffing / connections , usually the cause, if back not playing up isolated to front, unless you are giving a good hand full when braking, I found it not easy to get front abs to kick in, easier on back tho
    2003 GS Dakar
    BMW Panniers, top box, tank bag
    + loads TT stuff that came with it!

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  6. #4
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    cylindrical part highlighted = A remote reservoir shock is a shock damper that uses a remote reservoir to house a dividing piston that. separates the shock oil and pressurized gas (almost always nitrogen) within the reservoir.

    Std on Dakar not GS

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    Hi DakarDave - it looks like you're right - thanks for taking the time! //Derek

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    Hi KuyaJonathan!

    Thanks for the suggestion - I'll take a look later today, and give things another good clean just in case. Good point that isolation to front wheel would tend to indicate the fault lies there...

    Regarding the question of how hard I'm braking - the ABS effect (pumping in the brake lever, poor braking effect) occurs regardless of how hard I brake. In fact I even get it a slow/crawling speeds as I'm testing things in the car park where braking is hardly necessary because of the speed. Workaround for the moment is to turn off ABS...

    //Derek

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    Thanks for clarifying things Anthony - much appreciated.

    I'll have another look through the manuals. You can see attached Haynes manual doesn't show it in its illustration...

    GS Dakar in Haynes.jpg

    //Derek

  10. #8
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    Hi
    Are you sure it the ABS kicking in and not warped disc or caliper issue ? causing pulsing brake lever.
    But you did say it is ok with ABS off so possibly not the above.

    Would suggest sticking it on a GS911 or BMW diag to check front and rear sensor speeds. it might not be just front issue.
    Last edited by anthony; 04-08-2020 at 03:51 PM.

  11. #9
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    Hi Dereck,

    Could you describe your problem in a bit more detail please, because I might be able to help?

    The reason I ask is that my F650GS had an ABS problem when I bought it; the front brake lever would pulsate under normal braking but braking would then stop under heavy use. It turned out that there were two dings in the reluctor ring which resulted in brake lever pulsation due to the continual on-off signal from the sensor and then the complete loss of braking at low speed because the slower rotation meant the computer interpreted the break in the signal as wheel lockup. This was diagnosed by Steve Scriminger (well known and respected in BMW circles) and pressing the reluctor flat solved the problem.

    Regarding comparing the F650GS with another bike, even another BMW, is a little unfair: I have an R1200ST and it's a completely different beast to my GS - if I were going a long way on good roads I would choose the ST every time, but for local journeys and even long journeys on poor roads then I would pick the GS - horses for courses and both bikes do what they are good at very well.

  12. #10
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    Hi Andy, All that have helped,

    I've solved the problem and as you've suggested it was related to the sensor/reluctor. How the problem arose is still a mystery however.

    I live in Norway and the roads get icy in winter, and that's when I use the 650.

    I have 2 sets of wheels, one with studded tyres mounted, and I swap them around as the seasons dictate. The thing is that being a cheapskate I swap the disc and reluctor between front wheels at the same time as swapping he wheels over, so I know how they're mounted.

    You can see from the two "Reluctor" jpegs attached that there's wear where there's been contact with the sensor. When I took a close look the intermittent contact and poor alignment was clear to me. I removed the disc and found a bunch of shims had been installed behind the disc - it MUST have been done by the BMW workshop doing the work on my forks (certainly not by me)... The shims pushed the disc out of alignment!!! That was a surprise. I removed all the shims, re-installed the disc, checked the runout (perfect) and I've just come back from successfully testing perfectly functioning ABS brakes!

    Thanks to you all for taking the time to help!


    ABS Reluctor (1).jpgABS Reluctor (2).jpgDisc Shims (1).JPG

    //Derek

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