problem bleeding rear brakes on Sportster

Discussion in 'Other Service and Maintenance' started by rgooch, Aug 11, 2014.

  1. rgooch

    rgooch New Member

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    I rebuilt the master cylinder. I'm unable to get the brakes bled. Using a vacuum pump its not working. Emptied the reservior three times and still sucking air. Brake paddle still soft. Cylinder on caliper is pushing out with no presser. Pedal falls to the floor. No brake light.
     
  2. Jennmarr

    Jennmarr Junior Member

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    It has been my experience that the only way to reliably get that master cylinder bled is to open the bleeder screw, push the pedal down, and close the bleeder with the pedal depressed. Release the pedal, open the bleeder, depress the pedal, close the bleeder.....you get the picture. It is a slow, tedious process, but it will work.
     
  3. rgooch

    rgooch New Member

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    I've tired that. The pedal stays soft, no air comes out
     
  4. dbmg

    dbmg Experienced Member

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    Possible something is a miss with master and fluid is bypassing one of the seals....:(
    Can master be removed and tried to be bench bleed?
     
  5. Bodeen

    Bodeen Well-Known Member Staff Member Moderator Contributor

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    Sound like the master rebuild isn't quite right. May need to take it apart and inspect it carefully.
     
  6. Breeze3at

    Breeze3at Well-Known Member

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    I'll second that motion. Common problem is a nick in the piston oring/seal, or a bit of rubber in the return port.
     
  7. Jack Klarich

    Jack Klarich Expert Member

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    Harley Davidson Forums
    Read here
    Also with the cover off pump the brakes do you see bubbles coming out of the compensator port in the bottom of the cylinder? If you do not either rebuild again and clean the port or replace the master
     
  8. rgooch

    rgooch New Member

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    I tore apart the master cylinder in found the primary Cup was torn I was real careful when installing how can I be more careful
     
  9. dbmg

    dbmg Experienced Member

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    Saturate seal with brake fluid before installing..
     
  10. 03HD883R

    03HD883R Active Member

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    Yeah, if you saturate it, it acts like a lube and it makes it go better so it won't tear.