Author Topic: Air in Brake Lines  (Read 7523 times)

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  • Offline Asct17   us

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    Offline Asct17

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    Air in Brake Lines
    on: Oct 25, 2020, 07.20 pm
    Oct 25, 2020, 07.20 pm
    I recently bought a 2016-2017 Service Manual from Helminc.com for my 2017 VFR1200XD.

    For brake bleeding, the process is to drain the fluid from all the bleed valves before refilling with new fluid.  So, this is a two-step process: (1) Bleeding (2) Refilling.

    Do any of you find it a bit strange? 

    Most of the YouTube videos (for other bikes) caution against emptying the master cylinder to prevent air bubbles.  But if we drain the fluid completely, there will be plenty of air in the lines.  In the filling stage, the manual does caution against air bubbles.
    What's wrong with running the new fluid through the lines until the old one disappears?  Just remove the excess fluid from the master cylinder until it is at the low mark, then cycle the new fluid until clear fluid shows up without air bubbles. 

    I would appreciate any advice from the fellow members. Thank you for any input your could provide.  What are your experiences?  By the way, I have not started the bleeding process yet.
    Last Edit: Oct 25, 2020, 07.21 pm by Asct17

  • Offline Asct17   us

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    Offline Asct17

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    Re: Air in Brake Lines
    Reply #1 on: Oct 26, 2020, 12.37 am
    Oct 26, 2020, 12.37 am
    I might have found an answer to my question.  See the attached PDF.  I don't think these two pages are required.  If you are doing a complete drain, then these directions make sense.  If you are just replacing the old fluid with the new one, then don't let the reservoir go empty while bleeding.  This is what I think.  Feel free to comment.  Thanks.
    Last Edit: Oct 26, 2020, 12.41 am by Asct17

  • Offline Hartley   england

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    Offline Hartley

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    Re: Air in Brake Lines
    Reply #2 on: Oct 26, 2020, 09.55 am
    Oct 26, 2020, 09.55 am
    This is a procedure I’m planning to carry out soon. Fluid is starting look past it’s best.


  • Offline Jfro5867

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    Offline Jfro5867

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    Re: Air in Brake Lines
    Reply #3 on: Oct 26, 2020, 11.15 am
    Oct 26, 2020, 11.15 am
    I've seen this aswell, makes no sense whatsoever to me to introduce a problem that doesn't exist into your brake lines (air bubbles). Why empty the system?

    The tiny amount of old fluid left when you flush through new seems insignificant to me. We are not talking formula 1 here are we.

    Is it a cynical ploy to over complicate and force us to the dealers?

    I think it's going to be important to bleed in the correct order though, when the time comes due to the linked system. There's a few decent how to's on YouTube to give us a head start. If the system is the same as the ST1300Pan there's an excellent one for sure.


  • Offline Asct17   us

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    Offline Asct17

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    Re: Air in Brake Lines
    Reply #4 on: Oct 26, 2020, 02.01 pm
    Oct 26, 2020, 02.01 pm
    Thanks guys.
    I think the correct procedure is in CorrectBleedingSteps.pdf (see attached). 

    The previous PDF that I posted is for complete draining of the system.  I don't think the entire system needs to run dry as shown in my previous PDF.  I am assuming they listed it for some other reason.  I am planning to do this myself too.  Hartley have you done this before?  Let us know how did it go if you end up doing it before me.

  • Offline Hartley   england

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    Offline Hartley

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    Re: Air in Brake Lines
    Reply #5 on: Oct 26, 2020, 03.07 pm
    Oct 26, 2020, 03.07 pm
    Ascot,

    No mate not done it before, plan for over the winter.


  • Offline Asct17   us

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    Offline Asct17

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    Re: Air in Brake Lines
    Reply #6 on: Nov 04, 2020, 12.33 am
    Nov 04, 2020, 12.33 am
    I bled my brakes today.

    Equipment used:
    1.  20 gal air compressor.  4.0 SCFM at 90 PSI with 200 PSI max pressure.
    2.  Harbor freight brake bleeder kit
    3.  8 mm wrench
    4.  Phillips head screw driver
    5.  Brake fluid
    6.  Plenty of rags

    Bleed Sequence 1:
    Left front upper valve --> Right front valve --> Fill the front reservoir and install the cap.

    Bleed Sequence 2:
    Left front center valve --> Rear valve --> Fill the rear reservoir and install the cap.

    For the entire procedure, I did not let the system run dry.  I kept a close eye on the reservoir level.

    There were plenty of air bubbles and I paid no attention to them.  Once a couple of reservoirs were flushed (each for front and back), I closed the valve and pumped the lever.  Within a few pumps, the lever was solid.  So, this was my experience.  Your experience could be different.
    Last Edit: Nov 04, 2020, 12.39 am by Asct17

  • Offline Asct17   us

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    Offline Asct17

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    Re: Air in Brake Lines
    Reply #7 on: Nov 04, 2020, 07.15 pm
    Nov 04, 2020, 07.15 pm
    Just got back from a long ride.  No issues whatsoever.  Brakes are solid.  No warning indicators on the instrument panel. 

    Just wanted to clarify a bit more.  I flushed about 2 to 3 reservoir worth of fluid for each nipple.
    Last Edit: Nov 04, 2020, 07.26 pm by Asct17