Brake tears or My Airhead is Crying

Discussion in 'Airheads' started by More_Miles, Aug 30, 2010.

  1. More_Miles

    More_Miles über-n00b

    Joined:
    Aug 10, 2009
    Oddometer:
    362
    Location:
    New Brunswick Canada
    Howdy all!

    Bike: 1983 R100RT

    Symptom: Brake fluid seeping out of the reservoir on the bars. Appears to come out around the brake light switch, the actuator, the junction between the plastic reservoir and the metal base, etc. Only seems to do it when it's hot out or the reservoir is in the direct sunlight. Brake action is unimpaired, or at least not less inspired than it was when I bought it.

    I've looked at the parts schematic and I think I'm looking at three possibilities.

    1) I have a pin hole in the bottom of the reservoir :huh
    2) The O-ring (item 21 in this 'fische diagram, stolen shamelessly from A&S cycle for illustration purposes) is knackered
    3) Something is whacked with the piston assembly :cry
    [​IMG]

    Of all of these, I hope it's the O-ring, simple (read CHEAP) fix. After having a car once try and kill me with a catastrophic brake failure, I'm paranoid when it comes to the brake system!

    Anyone ever have a similar issue to this? Anyone know what size/material this O-ring is? It seems ludicrous to pay an arse-load of shipping for a $0.10 O-ring and the local Stealership is a 3 hour ride away. I don't want to get the assembly apart only to wait a week for parts... After all, my riding season is already too damn short!

    Cheers all!

    Craig
    #1
  2. AntonLargiader

    AntonLargiader Long timer

    Joined:
    Aug 28, 2003
    Oddometer:
    5,086
    Location:
    Charlottesville, VA
    It's most likely the piston combined with the bore of the MC. Get a new piston (you really want the seal but you have to buy the piston, at least from BMW) and then clean and thoroughly inspect the bore. If it's pitted, it can be bored and sleeved but you're approaching the cost of a new MC so it would be faster to return the piston at that point and order a new MC (you get the piston and reservoir also).

    Piston, about $70
    Sleeving the MC - $80.
    New MC - $190 or $200.
    #2
  3. coastranger

    coastranger Been here awhile

    Joined:
    Jun 16, 2009
    Oddometer:
    429
    Location:
    coast range oregon
    while Anton is most prob right, I had a similar leak, and conditions were about the same. And I woul donly find the leak ( seepage) in near the same location, after the bike had sat for a while,
    for me, fortunately it worked like magic, as I had (days before) rebuilt the mastr, I gambled , took it all apart , cleaned it, put it back togther and it was gone. never did find the true source

    brakes, toss up which is more important, brakes or getting it started, I would not rixe a street bike without fully functional brakes
    #3
  4. More_Miles

    More_Miles über-n00b

    Joined:
    Aug 10, 2009
    Oddometer:
    362
    Location:
    New Brunswick Canada
    Looks like I'll be doing some brake work. I'll probably just order up a new MC and install that, then look to see if rebuilding the old one is worth while. If it is then I'll have a spare and won't have a great amount of down time.

    Cheers all!

    Craig
    #4
  5. boxerboy81

    boxerboy81 Stay Horizontal

    Joined:
    Jul 22, 2009
    Oddometer:
    3,307
    Location:
    Melbourne, Oz
    Consider a 13mm or 14mm mc from the monolevers. I put a 13mm in my 1982 RS. Excellent mod imo.

    Good prices at Motobins.

    Progressive lever action, though a tad longer.

    Certainly much less abrupt than the 15mm oem mc on the twin shocks.

    You get used to the lever travel very quickly.
    #5