2002 Dual Front Brakes feel spongy

Discussion in 'Sportster Models' started by NYHarley, Jul 6, 2009.

  1. NYHarley

    NYHarley Active Member

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    I have a sporty with Dual Front Discs, and since I have had it the front brake seemed very spongy. Since the addition of my second Harley, I noticed that my single disc is alot stiffer. I changed / flushed the fluid in the Sporty today, and still have the same spongy feeling. I just need to know if that is normal or if there is something I need to do?
     
  2. martin14

    martin14 Active Member

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    open the master cylinder cap.
    fully engage the brake lever, then tie it off with a bungee or something.

    leave it overnight.

    In the morning, take a rubber mallet and -gently- tap the caliper and the
    brake line all the way up to the master.

    untie the brake lever, put the cap back on.

    spongy brakes is usually air in the brake line.
     
  3. NYHarley

    NYHarley Active Member

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    I did bleed the brakes today and it didn't look like there was any air in the system, unless it is in the lines, and not coming out.
     
  4. martin14

    martin14 Active Member

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    Thats what the tapping the lines is for, to get the air moving.


    By spongy I am guessing you mean the brakes dont start working until
    the lever is halfway depressed, you never seem to get full braking power,
    even with the lever full on.

    90% of the time thats a bit of air in the system.

    Only other suggestion is to remove the cap again, and pump the brakes
    until you can see the brake fluid jumping in the master cylinder..
    tapping the lines from time to time; just be careful you dont get brake fluid
    all over the bike.
     
  5. TQuentin1

    TQuentin1 Well-Known Member Staff Member Moderator

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    I have a '91 Dyna with single front brake rotor and caliper. I also have a '03 UC with dual fronts. There IS a big difference in the feel between the two. The single is much more positive with a firm feeling brake lever. The duals feel different and more mushy. I have fiddled with this chasing air in the system to no avail. Finally decided "that's the way it is!"

    TQ
     
  6. glider

    glider Veteran Member

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    Don't forget that with the dual systems you not only have a different size master cylinder but you are operating two calipers (the newer ones with 2 pistons each) and the associated double brake lines that expand a bit when pressurized so it's double everything of the single brake system.
     
  7. HD/OLD SCHOOL

    HD/OLD SCHOOL Member

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    Hello glider , speaking of brakes , i am getting ready to swap out my bars on my 09 sg . It has the dot 4 fluid , how potent is this fluid around painted surfaces ? How long does it take to cause a blimish ? Just in case i miss a spot while changing out the brake lines . Thanks , old school
     
  8. R. Lewis

    R. Lewis Senior Member Retired Moderators

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    Find some old towels/rags and cover up any painted surface that you can!
     
  9. glider

    glider Veteran Member

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    dot 4 IS not the silicone fluid that paint can tolerate. Cover the tank and fenders with something that the brake fluid will not penetrate and be careful too. It can mark the paint pretty fast if left on there.
     
  10. HD/OLD SCHOOL

    HD/OLD SCHOOL Member

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    Glider , thanks , the gas tank and front end is off right now , so i will cover the rest with painters plastic sheeting . Hd