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No resistance at front lever

Discussion in 'Technical and Troubleshooting Torque' started by port80, Feb 24, 2009.

  1. Last week I change the rear brake line over for a braided type. Easy job all done in 20 mins.

    Tonight I attempted the fronts. The HEL kit was of a slightly different design from the original kit as it split into two long lines from the master cylinder instead of splitting above the front guard.

    I emptied the old lines and emptied the master cylinder as best I could, took off the old lines and fitted the new. I found the HEL lines to not really be the perfect length and there were no routing instructions included.

    Next I filled up the master cylinder and then loosened the right caliper bleed nipple a half turn and started pumping through the new brake fluid. After a while I stopped getting air bubbles through, but there was next to no resistance at the lever. I figured that this was probably because the left line would be full of air.

    I repeated the process on the left line. There was still no resistance at the lever, so I checked all the bango bolts were tightened correctly and that there were no obvious leaks.

    I then bleed the right and left lines again. Still no resistance at the lever.

    Can I please have some suggestions on how to remedy this?
  2. Did you refit the reservoir cap?
  3. As yet, no.
  4. Then try refitting it and see if you can get pressure in the system then.
    Worked for me when I fitted HELs to the Kat a few weeks ago. Think it has something to do with the bypass valve on the front cylinder but to be honest I don't really know that much about how bike brakes work.
  5. No joy. I haven't had to refit it on any other bleeds to get pressure back into the system.

    Cap on and much lever action, stil no resistance. Might have to take the calipers off for an inspect.
  6. Unless fluid's leaking out of the pistons or hoses I would have thought a lack of pressure could only mean a problem with the master cylinder - after all if it's squeezing fluid it's got to be going somewhere.
    Only other thought would be to cable tie the brake lever to on and leave it overnight in case it is just air trapped somewhere in the lines still.
  7. My thoughts also. A little bit of fluid comes out when I do the bleed, but not as much as I think should.

    Am going to try that trick also. However the lever action isn't soft, it's non existant.

    I'm wondering if pumping the master cylinder with little fluid through it hasn't rooted up the rubbers.
  8. I've taken off the calipers and inspected the lines the full way. There doesn't appear to be any leaks. I put folded up paper in between the brake pads on both sides and then sqeezed the lever, there was hardly any force applied to the paper.
  9. ?? That's a strange symptom Port.

    Don't be sure you've removed all the air. Definitely try the bleeding again.

    Yeh I know, it's redundant advice, you've already thought of it...
  10. What's happening is that there is a lot of air in the system, and squeezing the lever simply closes up the air gap a little then it expands again, without actually pushing the air through. Get a big syringe from the chemist or vet and put a small piece of hose on the syringe. Get a syringe full of fluid, connect it to the bleed nipple on your caliper and reverse bleed them both with the cap off the reservoir. You may even need to disconnect calliper and/or master cylinder to ensure you don't have a bend in the line that will trap air.
  11. tighten nipple, squeeze lever, release nipple, tighten nipple - repeat.

    With a bit of patience, this sequence will work the air out without having it run back and forth in the lines.

    I said nipple in a sentence. :grin:
  12. You need to bleed the master cylinder at the top banjo fitting where the 2 hoses join the master.
    Bleed as normal using the banjo as a bleed screw. Trapped air will blow past the washers and fittings.
    Then bleed the calipers.
  13. Thanks for the replies guys. I left the lever pulled to the bars last night, now it takes two fingers to pull the lever to the bars. So despite my initial thoughts there must be lots of air still trapped in the system.

    I'm collecting the bits to have a crack at the method Dev suggested, will report back this arvo.

    Thanks for your input Chefie, but that didn't really help - now I just have sore nipples. But seriously I put half a bottle through the front lines using the traditional bleed method in search of air, but none was coming out.

    MSCRacing, I don't follow how to use the top banjo bolt as a bleed screw, can you please expand on it.
  14. Yep, you must bleed the M/C too. Apply pressure to the lever, and crack the bleed nipple on the M/C (or the banjo if there isn't a nipple) then tighten it again before the lever loses all pressure. Leaving the lever pulled to the bars gives the bubbles a chance to rise to the top, possible getting caught in the M/C. Bleeding traditionally, you're just trying to push the air the whole way through again.
  15. :shock:

    yeah sorry mate, didn't meant to tell you to suck an egg. It was late when i posted so i was too tired to write a florally speech with disclaimers and the what not.

    I've only ever used the method i described + perseverance + swearing + beer. So I'm learning a lot from this thread.

    ...i got you to say nipples on the www. You're now going to turn up in porno searches around the world, how cool is that?
  16. if the stuff above fails two things I found.

    1. bike master cylinders are pretty borderline from a volume point of view. some can't pump enough volume in one stroke to slide the pistons down the cylinders once they get a bit sticky. They just "rock" on the seals. So I've found that some bikes need to have 3 pads chocked with something whilst you pump one to the disc. Remove chocks progressively until they are all home.

    2. Air gets trapped at the top banjo bolt. You can't pump fast enough to get it down and it doesn't always come back past the master cylinder. With a ring spanner on the banjo bolt (make sue it is only "nip" tight to start with and put rags under/around it), pump the buggery out of the lever an hold it. Now loosen the bolt enough for the lever to come back to the bar. Tighten the banjo bolt and repeat until you have lever.

    You may need to do both of the above.

    Another trick is to pump the lever until you have pressure and tie it back over night. The pressure in the system can force small air bubble back past the master cylinder.
  17. Thanks for all the tips. I have a good feel at the lever now.

    After putting the calipers back on I tried Dev's suggestion. I still had no feel at the lever so I pumped the lever for a good few minutes as fast as I could. There was resistance but still a bit of spongeyness so I then I tried bleeding from the top banjo bolt. It was very messy but seemed to give good feel at the lever afterwards.

    A quick normal bleed presented no air, so I torqued everything back up and took it for a test ride.

    The test ride went well, there is now much better feel at the lever. Particularly towards the middle of an emergency brake when you're right on the edge of front tyre grip.
  18. Damn! Why couldn't this have happened when we did Dan's brakes. I love the way he responds to adversity!
  19. :rofl: :rofl: :rofl: Thanks for that, made my morning!!

    Seriously, I think the correct sequence is: Loosen nipple, pull lever in, tighten nipple, let lever out, loosen etc...
    Having two (coordinated!) people helps, if you can do it fairly quickly the air won't have time to bubble back up the hoses. Certainly good to bleed the master cylinder first via the banjo.
  20. Aha! well that would explain the sore nipples then. I'm never going to post at 1 o'clock in the morning again. :wink: