rear brake

Discussion in 'Crazy-Awesome almost Dakar racers (950/990cc)' started by vwboomer, Jun 27, 2013.

  1. vwboomer

    vwboomer Buffoon

    Joined:
    Feb 12, 2008
    Oddometer:
    11,426
    Location:
    WI
    I'm heading to CO next Thursday, and it appears my rear brake is mostly non functional. It worked before taking the wheel off for a tire change, the bike sat for two weeks waiting for the tire to show up, now very weak brakes. I tried new pads but no result. It doesn't really build pressure after pumping. I did try reverse bleeding and didn't notice a difference.

    Due to time constraints, I may not be able to get a master rebuild kit ordered and installed. Anyone know if they are just orings inside the master, or if they are cup seals? :ear

    It's the only thing I can think of to change.
    #1
  2. grant22

    grant22 Been here awhile

    Joined:
    Feb 22, 2013
    Oddometer:
    510
    Location:
    Lake Havasu, AZ
    Try doing the more traditional automotive method of bleeding: pump, pump, pump, hold, crack the bleed screw with hose. Repeat this while keeping the res full.

    It worked for me. Have a second set of hands tap the caliper and hose while doing this to help knock additional bubbles loose.
    #2
  3. vwboomer

    vwboomer Buffoon

    Joined:
    Feb 12, 2008
    Oddometer:
    11,426
    Location:
    WI
    I did try that method as well, to no avail. In the past when using the old school method I ended up needing to rebuild 2 calipers. Theory being the seals went outside the normal travel in the bore and got knicked. After rebuilding and bleeding the worked perfect. :dunno

    Picking up a different master after work this morning to try that out.
    #3
  4. Orangecicle

    Orangecicle On a "Quest"

    Joined:
    Apr 24, 2007
    Oddometer:
    3,463
    Location:
    West Des Moines, IA
    Do what you can to get that master working. I came down off of Mt. Evans two-up with my sister, and my rear brake failed. The problem was, the front brakes were warped and totally sucked. When you have those big elevation changes on a big heavy bike, you want all the brakes you can get. You might also try to remove the rear caliper and hold it upside down when you first start bleeding from the master. That can assure that you get any water out of the system. What happened to me on Evans was that I heated the rear to the boiling point, and I had water in the fluid. That turned into steam and poof, no brakes.
    #4
  5. benh

    benh lookin 4 a way outta town

    Joined:
    May 29, 2007
    Oddometer:
    262
    Location:
    Louisville, KY
    The rear brake on this bike is the most annoying part. My original master was so bad, I bled it and it would stay for awhile but eventually failed. I bought a new master cylinder and after 9 months it has started the same death dance.

    I feel like I am constantly bleeding the rear brake and it generally fades quickly. I had a Honda that I only once bled the rear brake only because the fluid was dark....however the brake functioned fine.

    I have a theory that since I have a stock exhaust that gets extremely hot especially in traffic on 90 deg day that the seals and fluid are breaking down quicker than expected. Or maybe I just really want an aftermarket exhaust.:D
    #5
  6. vwboomer

    vwboomer Buffoon

    Joined:
    Feb 12, 2008
    Oddometer:
    11,426
    Location:
    WI
    aftermarket exhaust likely would route the same way anway :dunno

    I put a whole new used rear assembly on and it works fine. Once I had the old unit off I could see it was wet on the bottom seal of the housing. A rebuild kit will be installed when I return, and the assembly will go back to its rightful owner (thanks CJ!)

    I also picked up a Rekluse. Oops!
    #6