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Help Any special trick to bleeding brakes?

Discussion in 'Tyres Wheels and Brakes' started by DamnitLaverty, Sep 8, 2016.

  1. DamnitLaverty

    DamnitLaverty Doing things the hard way since '78!

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    the brake piston seals you mean?

    No idea, I didn't tear apart the caliper... the old pads were down to a mil and a half though (from 4.5mm!)- it's totally possible when i cranked them open the seals went over some crap in the bore and failed. I'll check for leaks, etc tonight in the seals I guess.
     
  2. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    OK last tip, as you've obviously got the tools to vacuum bleed, do a reverse vacuum bleed.

    For this you'll need to use teflon tape to seal the bleed nipple screw threads, if you've got a screw cap fluid reservoir there will be a plumbing screw cap available to suit from bunnings etc.

    You put a small hole in the centre of the new cap for the master reservoir, seal with mastik or potentially blu-tac, run the tube to your vacuum system, a tube into a fluid reservoir on a caliper nipple, loosen slightly and start your vacuum system.

    The major benefit is that it draws upwards, which is the direction bubbles want to travel naturally
     
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  3. kiffsta

    kiffsta Senior Member

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    I have had a few sets that wouldn't bleed up after sitting for ages, most of the time it was bleed nipple, I replaced them and they came up fine.
     
  4. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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  5. DamnitLaverty

    DamnitLaverty Doing things the hard way since '78!

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    Ok. So Ninja 250 has the same bleeder screw, but the dust cap is different and sets above the hex, not under it.

    New bleeder didn't fix the problem, but better light confirmed the air is coming out of the screw, so I pulled the caliper off and actuated it. Only one piston is moving. Guess the piston nicked a seal when I fitted the new pads.

    Took the other side off, one is jammed there, too, but I must not have compromised a seal.

    Now to find rebuild kits for the calipers. At this rate I might not get to ride it until Halloween!

    Looks like US n250 calipers look the same but might have a piston difference so I don't think I can use those as replacements, and they're single-sided anyhow so that doesn't help. Ugh.
     
  6. kiffsta

    kiffsta Senior Member

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  7. DamnitLaverty

    DamnitLaverty Doing things the hard way since '78!

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    Nice! I've been taking part numbers to my guys, but they keep getting on me about the service manual only having 5 digit numbers! Guess I better start looking at ALL the books I downloaded, huh?
     
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  8. sharky

    sharky Well-Known Member

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    Jammed pistons are a common problem no need to rebuild just yet, try pulling the pistons out first and cleaning them too, theres usually a bit of pitting on the piston causing the sticking.
     
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  9. Johnny

    Johnny Well-Known Member Premium Member

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    I had this pressure problem recently on my Suzuki. I bleeded it to death, no pressure. Tied the lever down overnight, no pressure. Then I just started to pump the lever, with the M/C reservoir cap off but the bleed screw closed. Just pumped, pumped, pumped. Turned the handlebar to the right, then to the left, pumped the lever, tapped the brake hose, pumped again etc etc. Occasionally I saw small bubbles coming up to the M/C reservoir when I holded the brake lever down, this gave me confidence to continue. So I had to pump maybe 1000 times that lever, but at last I got the pressure. The thing is, when there's some stubborn bubble in the hose, it just stays there, I mean, it won't come out with bleeding, it just hangs out there somewhere in the hose.
     
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  10. rustguard

    rustguard Active Member

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    Motor bike and push bike brakes are mongrels to bleed, they need to be primed. A dead simple way I use everytime is to grab a 2 dollar syringe from the chemist (ask for their largest).
    Fill it up with fluid, then connect it to the open nipple with a bit of fuel or aquarium hose and give it an injection. sit the cap on top of the master cylinder as it might spray up of the reservoir. As you are pushing the fluid up there will be little if any air to bleed out.
    Quick, cheap and simple.
    wash the syringe out with water straight away it will be good for another use.
     
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  11. Murdo

    Murdo The Good Doctor Staff Member Contributing Member Ride and Events Crew

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    All of the above.
    One really stubborn one I had on my Yamaha Tenere, I had to unbolt the caliper and hold it up to the roof of the shed with a slice of wood between the pads. Left it overnight and was able to bleed out a serious bubble next day. Needed to have an assistant to pump the handle and fill the fluid while I bled it.
     
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  12. rustguard

    rustguard Active Member

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    yeah its amazing how one works around problems, Ive had scooters where I wasnt in a hurry so just strapped the lever to the grip and left em overnight.
    with regards to the syringe maybe I suck the fluid, or both, whatever workx is fine for me.
     

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