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Spongy Front Brake lever

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  • #1

    Spongy Front Brake lever

    Can anyone offer any advice on how to fix a spongy front brake lever on my '99 GSX750F? When I pull the brake the lever almost touches the accelerator before it kicks in, it actually pinches my index finger, I tend to kep my index finger wrapped around the accelerator. If I pump the lever really quick 2 - 3 times I get good firm feel in the lever, the way it should be.

    I've changed the pads and brake fluid, and have bleed them to the point where the new fluid has been changed again. I've ordered a new set of caliper seals and braided hoses, will this help?

    Any thoughts really appreciated!

    Regards

    Jim
    Tags: None
  • #2
    Bleed, bleed, and bleed again. Takes along time to get the air out. I will let gravity bleed out both calipers for awhile then you the old squeeze method. Just make sure to keep an eye on the resevoir so it doesn't go dry.
    Must read for carb tuners......http://www.factorypro.com/tech/tech_...m_engines.html

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    • #3
      it could be that the dust seal "seats" have got corrosion in them and pushed the dust seals out, which grabs the pistons ....

      when you squeeze the lever it pushes the pistons out but being as the d/seals are holding on , as soon as you release they pull the pistons back into the caliper body, which means you have to pump two or three times to get any bite..

      i've had this problem on three sets of calipers recently, the cure is to strip them and carefully scrape the seal recesses clear of corrosion, i use a small strip of 1-1.5mm thick sheet steel that i cut to almost a point then bend the last 3 or 4mm to 90 degrees to get into the seat where you can't see then fit new seals...

      a cheap fix can sometimes be (if the seals have exited the caliper body) is to pull the remains out carefully and run without them, i've managed to do this without stripping the calipers
      it ain't broke ....




      i ain't fixed it enough

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      • #4
        Originally posted by NiteMare View Post
        a cheap fix can sometimes be (if the seals have exited the caliper body) is to pull the remains out carefully and run without them, i've managed to do this without stripping the calipers
        YIKES ! your life depends on your brakes. do NOT run with your brakes not properly assembled or pieces missing. NiteMare, your name is highly appropriate for that bit of advice.

        In most all cases, a spongy brake lever is a function of air in the system (bleed bleed bleed, and bleed again), bad or old brake lines, bad master cylinder seals, or a combination of the above. Air is the most common.
        99% of the questions asked here can be answered by a 2 minute search in the service manual. Get a service manual, USE IT.
        1990 Suzuki GSX750F Katana
        '53 Ford F250 pickumuptruck
        Lookin for a new Enduro project

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        • #5
          Chances are you nned to bleed the master cylinder. It may have an air lock in there.
          Remove the cap and while you squeeze the lever, lightly tap the master cyclinder and look for tiny bubbles to come up from the bottom. you may need to adjust the steering at different points until air comes out.
          Sometimes you can get lucky and zip tie the lever to the grip overnight and the air will work its way up to the highest point.
          If not you will have to protect the painted surfaces reall well, wrap the front brak line with a rag and while holding the lever to the grip, crack loose the brake line bolt from the master cylinder then tighten it up before you let go of the lever.
          repeat this a couple times.
          The re-bleed both front brake calipers again
          98 GSX750F
          95 Honda VT600 vlx
          08 Tsu SX200

          HardlyDangerous Motosports

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          • #6
            Thanks for the advice, I've bled them several times now. During the week I plan to service the calipers, new seals etc, and fit braided hoses. Hopefully this will sort the problem out!

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            • #7
              Originally posted by Jim_C View Post
              Thanks for the advice, I've bled them several times now. During the week I plan to service the calipers, new seals etc, and fit braided hoses. Hopefully this will sort the problem out!
              Good deal! Stainless hoses make a huge difference. Make sure that there's no rust on the metal bars inside the caliper...use sandpaper or buy new if you have to. Also if your master had sludge in it, you'll need to clean that out too (I know mine did when I bought my bike).
              -
              -


              I poured spot remover on my dog. Now he's gone.

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              • #8
                When I bled my brakes last fall I kept having mush. Finally, I grabbed the lever HARD and it went to normal. I've had to do that in cars as well after a brake change.
                Pain is just weakness leaving the body.
                -Unknown Author

                The quarrels of lovers are the renewal of love.
                -Terence

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                • #9
                  1 st post, cut a guy some slack ...you probably have air in the MC it's not easily bled unless you rotate the MC a bit to make the connection to the brake hose lower...as long as the fitting is ABOVE the fluid level air will get trapped;by rotating the fitting so it's below the fluid level the air will be forced out while bleeding ( a lot less messier than loosening the fitting. If you replace your lines with SS lines you will run into this problem. Give it a try it can't hurt.

                  Good Luck

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