Reverse bleeding process

Discussion in 'Maintenance' started by BoroRich, May 14, 2020.

  1. BoroRich

    BoroRich Elite Member

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    Anyone done this before? I've fitted an Accossato MC to the bike and HEL lines so the system is totally dry. I've got one of these syringes that I was going to use.

    [​IMG]

    What's the process? Does the brake lever need to be pulled in when filling?

    Are there other methods that are better? I did my old blade with a Mityvac and it was a PIA so I just ended up bleeding conventionally.
     
  2. Slick

    Slick Elite Member

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    Didn't get on with reverse bleeding probably due to my cheapo kit, the tube came off the nipple and made a fecking mess!.
    Having just done this myself on dry lines I found doing it the conventional way and setting the level to max travel helps quicken the process
     
    #2 Slick, May 14, 2020
    Last edited: May 14, 2020
  3. Slick

    Slick Elite Member

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    Have a vacuum too but found you could never tell if it was air in the lines or it was sucking it from the nipples oooer.
    My preferred method are stahlbus speed bleeders but they dont work well on dry lines.
     
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  4. dern

    dern Active Member

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    The vacuum methods work best if you wrap the thread on the bleed nipples with ptfe tape.
     
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  5. Bikeboy

    Bikeboy Active Member

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    I mitivac .its a good way to move a larger volume of fluid and air.
    No dont pull the lever in. And keep an eye on the reservoir.. dont want to over flowing if you get distracted
     
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  6. Muffking

    Muffking God Like

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    If you're going from the bottom up then when ever I've done it I leave the brake lever alone and push fluid up the system from the calliper until it fills the reservoir. Then close the calliper nipple and bleed the master cylinder the usually way from the top, opening the m/c nipple as I pull the brake lever until fluid spits out the master cylinder nipple.
     
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  7. RR7

    RR7 New Member

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    I went through the wars with bleeding my front brakes last year.
    I have 3 RR7s so could tell back to back one had a less lever travel and felt better. I put it down to how I was bleeding.
    I bought vacuum bleeder tubes and two different auto vac-pumps. I tried every trick on the net. After wasting over a litre of fluid the lever hadn't improved one bit.
    I'd say reverse bleeding is not useful and the vertical nature of bike front brake lines means they self settle after a while anyway. The bubbles find their way to the caliper's nipple area and the master cylinder nipple. In my case I traced the softer lever feel to a difference in the Nissin push rod length.
     
  8. dern

    dern Active Member

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    Often tying the lever to the bar and leaving it over night solves many air bubble related issues.
     
  9. RR7

    RR7 New Member

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    I've tried that and it works, but after a few hours goes back how it was for some reason.
    A hydraulics guy told me it's because the seals are square, and needed that way to retract the pistons.
     
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  10. BoroRich

    BoroRich Elite Member

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    Well it all worked pretty well. Put the fluid in the MC and used the syringe to pull the fluid down to the calipers and out of the bleed nipple on the MC. Then just bled the whole thing using the traditional method. Didn't take very long to get a solid lever.

    Only problem I've got now is the wiring. Accossato has 3 wires. Blue, brown and black. Bike has two wires going to the switch. Green / White and Green / Yellow.

    Anyone got any idea what goes where?
     
  11. Muffking

    Muffking God Like

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    The M/C switch is probably 2-way. Do you have a multimeter to test which is Common, then it's just a case of working out which wire is push make and which is push to break. I think the bikes use push to make.

    Think of it a bit like this. The 3 wires on the M/C all connect to L1, Com & L2.
    Com is +12v and L1 or L2 is Neg.
    It doesn't matter which way round they go and if you get it wrong the hen the brake light will come on when you release the brake.
    [​IMG]
     
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  12. BoroRich

    BoroRich Elite Member

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    Thanks @Muffking. As you correctly summised :D One was push make and one was push break.

    Two other issues have arisen. The switch is only attached to the M/C with a flimsy push fit thing. Takes no encouragement for it to pop off :confused:

    And slightly more annoying. I've got the system all nicely bled but there's a weep coming from the threads of the M/C bleed screw :mad:

    I know I can solve it with some PTFE tape but I guess that means draining and pretty much starting again.

    [​IMG]
     
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  13. Muffking

    Muffking God Like

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    I'm not sure you have to start again. I think you'll get away with just bleeding the M/C again.
     
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  14. BoroRich

    BoroRich Elite Member

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    @Muffking If I remove the bleed screw from the MC won't fluid start pouring out of it?
     
  15. Muffking

    Muffking God Like

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    Only if you pull on the brake lever.
     
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  16. BoroRich

    BoroRich Elite Member

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    Thank you all for your help on this one @Muffking @Slick @RR7 @dern @Bikeboy

    Just FYI that Sealey VS404 syringe is brilliant. Figured since I was arsing around with brake fluid I'd change the stuff out of the back brake too. The syringe is large enough to use one-handed and seals well over the nipple so you can pull back to create the suction and then just crack open the bleed nipple. No air came through. Just fluid. You can just top up the reservoir and watch the fluid go down. Took about 5 minutes to swap the fluid out. No hassle whatsoever.
     
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  17. Jez

    Jez Active Member

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    Before removing bits of the brake system I would remove master cyl screw lid and put poythene on top then screw the lid back on, this will reduce the leakage
     
  18. BoroRich

    BoroRich Elite Member

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    I think you might be thinking of the brake fluid reservoir rather than the master cylinder?
     
  19. Jez

    Jez Active Member

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    Hi, The trouble about giving advise is how knowledgeable others are, when I said master cyl screw lid, Yes this is master cyl res lid..
     
  20. BoroRich

    BoroRich Elite Member

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    Just for anyone who's interested. Well happy with the results of the MC, HEL braided lines and fluid change. Braking performance feels improved. So much so that I gave the front brakes a dab when I first went out and smacked my nuts into the tank :D

    Also, my rear brake was previously pretty useless. After swapping the fluid out it's back to spot-on. And that only took 5 minutes with the Sealey syringe.
     

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