Front brake master cylinder rebuild kit

Discussion in 'GS Boxers' started by -E-, Mar 11, 2018.

  1. -E-

    -E- Klaatu barada nikto

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    I must suck a searches. I cannot find a rebuild kit for the front brake master cylinder on my non ABS 2007 GSA. It would be much appreciated if someone could link me to a rebuild kit.

    Thanks in advance.
    #1
  2. OzRider64

    OzRider64 Friggen slow Adventurer.

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    As far as I know, you have to purchase the complete unit.
    The days when I had my 86 K100RS you could purchase a rebuild kit.
    On the newer stuff it’s a new unit only, bummer.
    #2
  3. GeorgeKingGeorge

    GeorgeKingGeorge Been here awhile

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    My experience as well. Rebuild kits are no longer available.

    You can always confirm this my calling your local dealer's parts department.
    #3
  4. -E-

    -E- Klaatu barada nikto

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    That sucks. Magura rebuild kits are available for other manufactures.
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  5. GeorgeKingGeorge

    GeorgeKingGeorge Been here awhile

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    Yep. i think it is because of the crappy material BMW uses in the master cylinder. The master cylinder on my K75 failed several years back. I tried to get a rebuild kit from the dealer but with no luck. They explain that the bore usually pitted and made rebuilding impossible. Sure enough, I pulled it apart and there was significant pitting in the cylinder bore. I'm assuming it was corrosion because of water in the fluid despite annual brake fluid changes. A new seal on the piston would not have lasted.
    #5
  6. -E-

    -E- Klaatu barada nikto

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    The master cylinder is a Magura part purchased from BMW. I expect Magura uses the same material in all their products. A worn piston seal does not always mean a damaged cylinder wall. Having successfully rebuilt Magura master cylinders on KTMs I expect this shouldn't be any different. Pitting is possible but shouldn't be assumed.

    Looks like the real issue is BMW wants to make a buck.
    https://www.beemerboneyard.com/mamacykifr3.html
    Note they still have rebuild kits for the K75.
    #6
  7. motoxfox

    motoxfox Been here awhile

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    A good machine shop will be able to 'line bore' the cylinder and re-sleeve with a S/S insert.

    If your piston is still serviceable a lite hone with wet & dry, re cup (piston seals).
    You sould be able to source these via the Magura parts manuals or generic supply based on O/D & I/D of the cup(s).

    Prime the M/Cyl with fresh brake fluid and bleed PRIOR to refitting to bike & brake line.
    Then go thru the bleeding of the full system.
    And you should be ready to go.

    This rework should now outlast the bike...and be less than the OEM part and attempt at Grand Larceny ! :)
    #7