Front brake issue: Possible airleak?

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    #1

    Front brake issue: Possible airleak?

    Ive been trying for days to get my front brakes on my gs850 working properly. I can buildup pressure if I pump the brakes enough times but if i let them sit for a few seconds they will go back to being spongey. The calipers have been rebuilt and there doesnt seem to be any fluid leaking from the calipers I have bled the brakes numerous times and there are no fluid leaks along the lines and joints. I am at wits end here!! Any ideas on what could be going on?
  • GSXR7ED
    Forum LongTimer
    Past Site Supporter
    • Dec 2012
    • 10147
    • DE via L.A.

    #2
    I have the opposite...I can't get any pressure. I'll have to remove the caliper and double-check the seal that wraps around the piston. I had a bear of a time getting it to fit properly and now I see why it needs to seat correctly.

    Good luck figuring it out...maybe you need to EVAL and check all the seals.


    Ed
    GS750TZ V&H/4-1, Progressive Shocks, Rebuilt MC/braided line, Tarozzi Stabilizer[Seq#2312]
    GS750TZ Parts Bike [Seq#6036]
    GSX-R750Y (Sold)

    my opinion shouldn't be taken as gospel or in any way that would lead you to believe otherwise (30Sep2021)

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    • GSX1000E

      #3
      Most likely, one of the seals in the master cylinder has a rupture/tear and the fluid is by-passing internally. Or installed backwards. Has anyone been inside it? Not too difficult to repair.

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      • jwhelan65

        #4
        Can you post a pic of your caliper?

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        • Nessism
          Forum LongTimer
          GSResource Superstar
          Past Site Supporter
          Super Site Supporter
          • Mar 2006
          • 35793
          • Torrance, CA

          #5
          Did you use OEM caliper seals or K&L? I've seen this with aftermarket seals because they were too tight and wouldn't let the piston adjust to the proper position away from the disc.
          Ed

          To measure is to know.

          Mikuni O-ring Kits For Sale...https://www.thegsresources.com/_foru...ts#post1703182

          Top Newbie Mistakes thread...http://www.thegsresources.com/_forum...d.php?t=171846

          Carb rebuild tutorial...https://gsarchive.bwringer.com/mtsac...d_Tutorial.pdf

          KZ750E Rebuild Thread...http://www.thegsresources.com/_forum...0-Resurrection

          Comment

          • GSXR7ED
            Forum LongTimer
            Past Site Supporter
            • Dec 2012
            • 10147
            • DE via L.A.

            #6
            ***Informational Only***

            While we're waiting for OP to post up pics and since this is relevant, here's my install of OEM parts for my caliper. I think when you look at the last pic you'll notice I don't have a proper seal.













            I'll remove the caliper and get a better seal today.


            Ed
            GS750TZ V&H/4-1, Progressive Shocks, Rebuilt MC/braided line, Tarozzi Stabilizer[Seq#2312]
            GS750TZ Parts Bike [Seq#6036]
            GSX-R750Y (Sold)

            my opinion shouldn't be taken as gospel or in any way that would lead you to believe otherwise (30Sep2021)

            Comment

            • jsandidge
              Forum Sage
              Past Site Supporter
              • Jun 2013
              • 1482
              • Norfolk, Virginia

              #7
              tutorial

              There's a tutorial on BassCliff's site showing how to properly install that dust seal. You should be putting it into the caliper groove first, then finagle the piston in. The dust seal will snap into the groove in the piston once you push it down all the way. Check out the tutorial, it has good pics.
              https://drive.google.com/open?id=0B9zH8w8Civs8ejBJWjdvYi1LNTg&resourcekey=0-hlJp0Yc4K_VN9g7Jyy4KQg&authuser=fussbucket_1%40msn.com&usp=drive_fs
              1983 GS750ED-Horsetraded for the Ironhead
              1981 HD XLH

              Drew's 850 L Restoration

              Drew's 83 750E Project

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              • Nessism
                Forum LongTimer
                GSResource Superstar
                Past Site Supporter
                Super Site Supporter
                • Mar 2006
                • 35793
                • Torrance, CA

                #8
                Install the dust boot over the piston and slide it down as far as you can. Then put the boot into the caliper groove before you install the piston into the caliper bore. Brake fluid lube will help the parts slide together. Once the piston is in the bore there is almost no way to get the boot into the caliper groove, it must be installed prior.
                Ed

                To measure is to know.

                Mikuni O-ring Kits For Sale...https://www.thegsresources.com/_foru...ts#post1703182

                Top Newbie Mistakes thread...http://www.thegsresources.com/_forum...d.php?t=171846

                Carb rebuild tutorial...https://gsarchive.bwringer.com/mtsac...d_Tutorial.pdf

                KZ750E Rebuild Thread...http://www.thegsresources.com/_forum...0-Resurrection

                Comment

                • GSXR7ED
                  Forum LongTimer
                  Past Site Supporter
                  • Dec 2012
                  • 10147
                  • DE via L.A.

                  #9
                  Thanks guys...and OP...look at the tutorial...we both need to learn something here.


                  Ed
                  GS750TZ V&H/4-1, Progressive Shocks, Rebuilt MC/braided line, Tarozzi Stabilizer[Seq#2312]
                  GS750TZ Parts Bike [Seq#6036]
                  GSX-R750Y (Sold)

                  my opinion shouldn't be taken as gospel or in any way that would lead you to believe otherwise (30Sep2021)

                  Comment

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