R1100GS front brake master cylinder....

Discussion in 'GS Boxers' started by Manuel Garcia O'Kely, Jan 25, 2013.

  1. Manuel Garcia O'Kely

    Manuel Garcia O'Kely Back at last

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    So I gave my son my R1100GS, since I'm not using it anymore, and he's in need of a road bike.

    However, the front master cylinder is leaking and the goo has also ruined the brake light switch.

    I've looked thru several pages here - anyone suggest a good place to get a used, working replacement or a new one for less than the silly prices the dealer wants? It's a 1998 so it's rather an antique by BMW standards.

    I see Beemer Boneyard has rebuild kits.

    Any other good thoughts?
    #1
  2. Pekkavee

    Pekkavee Been here awhile

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    #2
  3. Manuel Garcia O'Kely

    Manuel Garcia O'Kely Back at last

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    Should have thought of e-bay. I sent him that idea.

    Also, I agree that rebuild might be easier - I think he is hesitant to do something that safety-related to his bike - and I can relate to that.
    #3
  4. wvrocks

    wvrocks Been here awhile

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  5. Manuel Garcia O'Kely

    Manuel Garcia O'Kely Back at last

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    Advrider comes thru again. And in less than a hour.

    Thanks much, I sent him a copy of that link, looks like just what he needs.
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  6. def

    def Ginger th wonder dog

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    I would start by disassembling the OE piece and determine just what is damaged or needs replacement. The switch may be OK and only need some spray cleaner and follow up with silicone spray lubricant. The leaking stuff? Sounds like the piston seal in the master cylinder needs attention. A used part may be no better that what you have currently.
    #6
  7. Manuel Garcia O'Kely

    Manuel Garcia O'Kely Back at last

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    Agreed. Think we will get that cosmetic second from B. Boneyard.

    Unless you can inspect the part prior to delivery eh?
    #7
  8. Shango

    Shango Hi

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    I just did this a short while ago... The fluid ruins the switch so I got a replacement one at Radio Shack for about $4. You just have to cut the wires at the old switch and soldier on the new switch. Even the holes were in the right place for mounting it back on.
    #8
  9. Dan Cãta

    Dan Cãta Long timer

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    The piston seal started leaking on my GS too. What I did was to take everything apart, clean the inside and put it all back together. This stopped leaking for about 3 4 months and then it started again. I replaced the piston and seal (as a kit) and it worked fine since. Sold the bike in the meantime.

    Dan.
    #9
  10. vintagerider

    vintagerider Long timer

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    The 1100 mcyl was orig non-anodized inside. It is easy to tell if yours is anodized, just look in the reservoir. If the site glass shows no evidence of corrosion then you an save yourself a lot of work by removing the piston with the assembly still on the bar. The lever comes off and there is a very small bolt that retains the piston. From the outside of the m. cyl withdraw this tiny bolt and the one piece piston assembly can be removed for cleaning. There is often an accumulation of dried fluid that hinders withdrawal. Air pressure may be introduced at the banjo connection.

    Often it is just the cleaning as long as the site glass is not leaking. An alcohol bottle with snake bit foil is best for cleaning.
    #10
  11. Mr Puffin

    Mr Puffin Been here awhile

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    This worked well for me too :D I dismantled and cleaned mine, there was indeed an accumulation of debris, dried fluid or whatever it was. After cleaning out no leak :clap
    #11
  12. playinatwork

    playinatwork Been here awhile

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    I received one of the Beemer boneyard ones that was listed as having paint issues. I had to look long and hard at it to tell it wasn't perfect. It works like a new one should.
    #12
  13. def

    def Ginger th wonder dog

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    #13
  14. a1fa

    a1fa Throttle Jockey™

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    Well, I'll be damned. My master cylinder on the 96 started leaking again. This is after I rebuilt it using beemerboneyard rubber grommets. This could easily turn into $350 replacement. I guess I will re-open the master cylinder, and clean it up again, and sand and polish the cyl a bit more.
    #14
  15. a1fa

    a1fa Throttle Jockey™

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    Bore sanded, and polished again. We'll see if it holds.
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  16. a1fa

    a1fa Throttle Jockey™

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    I hate the way my front brake feels. No where near as smooth (mushy) as my 2000 R1100R. Same master cyl. Decided to crack open the R's M/C.

    [​IMG]

    Fork :) Lucky, this m/c was anodized, and this is all from the spring. Does anyone sell the spring individually?
    #16
  17. mouthfulloflake

    mouthfulloflake Not afraid

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    i would like to have a slightly stiffer one in stainless

    if you measure yours maybe we could source one via mcmastercarr or similar
    #17
  18. CopperGreen

    CopperGreen Been here awhile

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    I read a dia. of 0.358", length at 1.570" and wire dia at 0.040".
    Century Spring might be a better source-
    The fit in the piston is precise. Any alternate spring should be under the 0.358" dia. Length is not so important. Something like 1.625" or even 1.75" should work.
    But I agree- a stiffer stst spring would be the ticket.

    I found this...
    https://www.centuryspring.com/Store/item_detail.php?StockNumber=KK-73
    While not Stan Lewis, (StSt) it may just fit the bill....

    Let me add that along with the rebuild kit, go ahead and buy a new "boot". Mine was stiff and old. Replacing it with new, soft and supple one helps....
    #18
  19. a1fa

    a1fa Throttle Jockey™

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    My GS has a very stiff front brake, so I cracked it open, again to figure out why its stiff. It's not the master cylinder. Master Cyl is silky smooth. It's something to do with the pads, calipers. I run out of talent in figuring it out, and let it be. The R and the GS have same calipers.

    The GS (34112333111 CALIPER WITH OUT BRAKE PADS LEFT - D=32/34MM)
    The R (34112333111 CALIPER WITH OUT BRAKE PADS LEFT - D=32/34MM)

    Now with both bikes sporting Galfer SS Front Brake lines (same part number/ GS lines on both), I expected the brake feel to be the same. Yet, the GS is very stiff with very little travel - I ensured m/c piston stop screw is not binding; while R has some smooth travel. Braking feels the same between the two bikes.. A bit more meat on the GS pads.

    Now I am waiting to see if GS M/C will leak again.

    [​IMG]
    #19
  20. cds247

    cds247 Long timer

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    Brake, not break. To help with searching, if nothing else.
    #20