MC Reservoir leak: home-made gasket?

Discussion in 'Motorbike Technical Discussion' started by Brent, Jul 14, 2003.

  1. Brent

    Brent Guest

    The Master cylinder on my wife's CX500 leaks occasionally. I replaced the
    o-ring on the reservoir, with no real effect. The leak appears to be from
    the top of the reservoir/cover area. When the bars are turned at various
    angles, the reservoir is no longer level, of course, and the brake fluid
    reaches the top of the reservoir.

    There is no diaphragm or gasket there to ensure a tight fit on those
    surfaces. Any reason I couldn't cut a gasket from a piece of bicycle inner
    Brent, Jul 14, 2003
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  2. Brent

    Dan Carter Guest

    I suspect there should be a diaphragm. All of my Hondas (including an
    '83 CX650 Turbo) have had them. Check the parts diagram at your dealer.

    Before resorting to bicycle tube material, soak a sample in brake fluid
    for a couple of weeks to make sure it's compatible.
    Dan Carter, Jul 14, 2003
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  3. Brent

    Dave Guest

    I don't think it will stand up to brake fluid. Brake fluid is nasty stuff
    and you will need some type polymer that is made to resist deterioration.

    Dave, Jul 15, 2003
  4. If there's any place on the whole bike that doesn't seem like a good
    place for experiments, I think this is it.

    On my bike, (not a CX500), there's a rubber bellows thingie
    that sits at the top of the cylinder. Why not beg your dealer
    for a peek at the parts fiche and then replace the suspect parts
    with stock new ones.
    r_kleinschmidt, Jul 15, 2003
  5. Brent

    Fred Guest


    Not being able to go cannot kill you.

    Not being able to stop CAN!

    And inner tube rubber will NOT stand up to brake fluid. On any type of
    fluid reservoir there will always be at least an O ring or gasket.
    Someone probably removed it. A new oil ring or diaphragm will probably
    cost $10-15 but even if it's $20-25 it is worth it not to mess with
    the brakes.

    Fred, Jul 15, 2003
  6. Brent

    Brent Guest

    OK, thanks for all the helpful comments. I kind of knew the answer before I
    asked. Appreciate the re-inforcement, though.
    Brent, Jul 15, 2003
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