Re: LRO: CB Brake Master Cylinders

From: David Scheidt (dscheidt@tumbolia.com)
Date: Wed Apr 25 2001 - 13:54:55 EDT

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    On Wed, 25 Apr 2001, Mark Pilkington wrote:

    :I can pump up the pressure and it will hit the floor a few times then
    :hold. When holding, it will not fade, it will hold. Subsequent pumps
    :willk also hold without fading and the brakes are strong. BUT if I let
    :off the pedal and leave it for a few miniutes and then press it again,
    :it will go to the floor again until I pump it. It is a new CB master
    :type cylinder.

    First thing to do is figure out where the air is. Put a set of brake hose
    clamps on each of the flex hoses. If there is no air in the master, the
    pedal will be rock hard. If it's not, there's air in the master. You can
    try bleeding it by slacking off the output pipe a tad. Keep the brake fluid
    off the paint, of course.

    If the pedal is rock hard, then you have air in one or more wheel
    cylinders, worn shoes, oversized drumbs, incorrectly installed shoes,
    or the wrong wheel cylinders. If this is a 109, you might have an 88
    master cylinder. If it's an 88, the pin that the shoes pivot on may be
    loose on the backplates. Go to the wheel with the shortest run of brake
    pipe (the front right, I'd think) and adjust the brakes as tight as you can
    get them. You shouldn't be able to turn the wheel at all. If you can,
    you've got oversized drums, worn out shoes, or bad adjusters, or all three.
    Take off the clamp on that wheel's hose. The pedal should still be hard,
    but a little bit of movement is okay. If it moves more than that, there's
    air. Bleed. Put the clamp back on, and repeat for the other wheel. Then
    do the back axle.

    Take the clamps off, and you should have a good pedal. Adjust all the
    brakes properly, and you should still have a good pedal. If you don't
    you've got a mechanical problem -- 88 master on a 109, shoes on wrong, worn
    out shoes, pivot pin movement on the back plate. If this is an 88, see if
    the brakes work in reverse better than they do forwards. If they do, than
    the pivot pins on the backplate are probably moving.

    David

    -- 
    dscheidt@tumbolia.com
    Bipedalism is only a fad.
    



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