Brake Bleed Issue

Discussion in '1st & 2nd Generation 1983-1989' started by straycat, Apr 10, 2020.

  1. straycat

    straycat New Member

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    Not a VFR but I appreciate the experience of you guys on my problem.

    On My 2000 RC51, the brake lever was nice and firm, but.... the fluid was old & brown. On top of that I needed to put new pads in it too.

    I cleaned the calliper pistons, but didn’t remove them. Pushed them back in after cleaning and installed new pads. I bled the brakes like I have many many times, never let the fluid get too low, used pressure bleed method.

    but...now the lever feels very spongy and it now also creaks and makes a noise at the lever/master cylinder, almost like the Super DOT4 fluid doesnt lubricate the rubber plunger enough. it wasnt doing that before the fluid change.

    I can get it to firm up a bit if I pump it a few times, but it goes soft again after a while.

    Ive re bled 3x

    No bubbles at all, not a one.

    Im wondering if I have dirt/corrosion binding the calliper pistons and they are sticking, maybe not retracting all the way ?

    Ive tied the lever back over night and its firm after I do that but goes soft again after a short while

    Thoughts?
     
    Last edited: Apr 10, 2020
  2. squirrelman

    squirrelman Member

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    i've had good luck by removing the mc from the bar and holding it vertically, suspended from the lever while tapping the line to jiggle bubbles up and out. sometimes helps to remove calipers and hold them at different angles while tapping.

    sometimes it helps to squeeze the lever and crack the banjo bolt.

    u outta be able to see pistons move back just a fraction after letting off the lever.

    if nothing else helps u can try injecting dot4 with a syringe at any bleed nipple .

    some will say mittyvac, but i've never needed it.
     
    Last edited: Apr 10, 2020
  3. straycat

    straycat New Member

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    Thanks squirrelman. ill try that !

    I have a mityvac but I find it sucks more air past the edge of the bleed nipple and you can never tell when the bubbles are from the calliper, so I tend not to use it much
     
  4. raYzerman

    raYzerman Insider

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    Once the system is filled (say when fitting new lines or caliper rebuilds), SpeedBleeders work great. I've had mixed results with vac bleeders, don't use them any more, have their place if filling a system. Remove your calipers, leave pads in, pump until the pistons expose themselves more, clean the pistons etc., (I usually use a toothbrush, dry, with brake fluid, then rinse with isopropanol). Remove your levers, lube the pivots with silicone grease (won't wash out), and check that brass bushing on the clutch side, if worn, get a new one. That's likely where the squeaks are, doubt it's the rubbers. Once bled, tie the levers to the bar overnight, air will be compressed and likely move up to the reservoirs, or in the case of a PVC, to the high point. Rear caliper on a Gen5, e.g., I remove it and hang it up high. Quick bleed after that to confirm air out. Speedbleeders have thread sealer, you can wrap existing bleeders with Teflon tape on the threads or use grease around them, which of course you clean off later with isopropanol.
    Quick bleed every year as prevention and to have fresh fluid.
     
  5. straycat

    straycat New Member

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    thanks !

    I did the above quoted steps already, but it wont hurt to do it again.

    I too use a tooth brush and brake clean, will try the brake fluid and iso
     
    Last edited: Apr 11, 2020
  6. straycat

    straycat New Member

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    Gonna order some rebuild kits and to the MC and callipers. Caliper joint bolts look like shit anyway so they have to come out and be replaced with Stainless. may as well re do the lot
     
    Last edited: Apr 19, 2020
  7. Colddevil

    Colddevil New Member

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    I've found that switching the line to stiff 1/4" fuel line and tying a zip tie around the end I can stop any air slipping past. This doesn't solve your issue, but it may help if you're having issues with the line slipping off the bleeder. It's tough to get it onto the bleeder, but once it's on, it's there.
     

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  8. straycat

    straycat New Member

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    yea, thanks, I have used the zip tie when I tried to back bleed (different bike) , but to be honest, I have never had success back bleeding, I could never get the fluid to the master, maybe im just not doing it right.
     
  9. Colddevil

    Colddevil New Member

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    Gotcha. I'm having a hell of a time getting any pressure in my brakes at the moment, so I'm not a great resource. The back bleeding through the system to the top banjo using a syringe and zip-tied hose is about the only thing I've had any success doing, so I thought it might be relevant.
     
  10. straycat

    straycat New Member

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    Thanks, I may try it again, we will see one all the new bolts arrive. I may dismantle the callipers and the master to clean them and try them again as is.

    Ive only ever had issues bleeding Honda brakes (All Nissin ?), probably just coincidence. Ive bled a lot of brakes and clutches and only had problems on my 500 Interceptor (now sold) and this RC51.
     
  11. raYzerman

    raYzerman Insider

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    1/8" or 3mm ID silicone tubing stays on bleeder nipples.. SpeedBleeder sells it as well.
     
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