Forums 🚥 THE PiT STOP 🔧 Hyosung Technical Help How to change Vacuum Lines on Hyosung GT125R GT250R & GT Comet (Air Hose Diagram)

This topic contains 7 replies, has 2 voices, and was last updated by  ♠️ MARCEL 3 months ago.

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  • #1895

    ♠️ MARCEL
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    Changing the vacuum Lines on carburetor 125/250 vTwins, should be fairly easy. All you need is 15-30 mins of your time, let’s start with the basics first.

    • Hyosung says if your “standard” factory lines are 2-4yrs old.   Discard them regardless. 
    • Old pipes can also rot inside , especially those chinese ones with trashy rubber
    • Larger colder air pipes can help improve the vacuum system but get strong clips!
    • Strong clips are very essential to avoid all possible air leaks.
    • This tutorial applies to all carb operated 125/250  GT & GTR Twins  (includes GV125 too)

    Let’s go now…  Strip your fairings down  (GTR owners)   
    (if you have a naked bike,  go to next step)
    hyosung gt125r air vacuum line gt250 gv125

     

    Below is a diagram of how the “AIR LINE” system should be connected.
     Study (look at) the diagram images below first  , before moving on to the next step….
    //
    //
    hyosung gt125r air vacuum line gt250 gv125 hyosung gt125r air vacuum line gt250 gv125

     

     

     VACUUM LINE #1  = CONNECT  THE REAR FUEL PUMP  FIRST
    Got your lines ready?   
    On the LEFT side of your bike Grab a hose for the fuel pump & follow the next diagram pictures below:

    hyosung gt125r air vacuum line gt250 gv125 hyosung gt125r air vacuum line gt250 gv125 hyosung gt125r air vacuum line gt250 gv125

     

      VACUUM LINE #2  = CONNECT YOUR FUEL TANK TAP
    * Once your rear fuel pump  is connect from the left side.
    * Now, move on the the RIGHT SIDE of your bike
    * Grab a second vacuum pipe and follow the next diagram images below:

    hyosung gt125r air vacuum line gt250 gv125
    hyosung gt125r air vacuum line gt250 gv125

     

    That’s It – Vacuum Setup is done! 🚦
    However, if you have an AIS Device (Fake emissions/EGR) then read below!



    *Remember above ^ , there is a cartoon diagram of the infamous “EGR DELETE” mod, right ?
    *Remove it or block anything that feeds it.
    *This image is another example for you.
    * Personally, it’s a useless device. 
    * But, if you want it connected -> replace “blocked” with “connected”
    //


     

        Alright, we are done.   Go test ride! 🏁  

     


    I hope this fast toturial was easy to follow,  however if you get stuck or need help. Just comment on this post!  This tutorial should also help GV owners since they use the same rear pump anyway.

    // Meditation doesn't mean you have to sit still....

  • #1918

    shane
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    Confused with the first as it says connect pipe from fuel pump to Intake boot do I connect directly to the rear intake boot or the t junction rear pump connector

     

    And 2nd pipe from tank then do I connect to the hole of the one being removed

  • #1919

    shane
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    I’m guessing the centre pipe as a splitter before the t junction

  • #1920

    ♠️ MARCEL
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    I’m guessing the centre pipe as a splitter before the t junction

     

    Just repeating what was on the 2D diagram but in another way to explain it 👍

    INTAKE MANIFOLDS. (VACUUM ROUTING)

    =REAR HOLE 1 = Fuel Tap (small port under tank)

    =REAR HOLE 2 — JOINS WITH —- FRONT HOLE.

    (In other words = Rear #2 & Front Hole are joined with a T PIECE junction.)

    Front intake boot always has 1 hole.

    The back has 2.

    The vacuum pump wants both 1 rear and 1 front to work properly.

    Tank Tap goes up un 2nd extra free hole given by the rear.

    // Meditation doesn't mean you have to sit still....

  • #1922

    shane
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    also I just found mine as a fake egr but can I leave it installed as it is or does it after be blocked

    just if it doesn’t make a difference I was thinking of just leaving pipes connected to it saves me the hassle getting stuff to block the pipe etc

  • #1923

    ♠️ MARCEL
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    1. also I just found mine as a fake egr but can I leave it installed as it is or does it after be blocked just if it doesn’t make a difference I was thinking of just leaving pipes connected to it saves me the hassle getting stuff to block the pipe etc

    These links may help.

    https://m.facebook.com/groups/345623961212?view=permalink&id=10154901704736213

    https://m.facebook.com/groups/345623961212?view=permalink&id=10154883738251213

    That device is for euro tree huggers.  Very early GT/GV bikes didnt have them.

    Put simply. Bin it = bike is a *little* more throaty and gets rid of pops.

    Very common mod on 650s.  The forum has an EGR removal toturial for 650 but principal is the same on 125s.

     

    It is as useless as the sidestand switch 😉

     

    // Meditation doesn't mean you have to sit still....

  • #1924

    shane
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    so it just simple as getting a bolt to push into the tube and clamp it

  • #1925

    ♠️ MARCEL
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    so it just simple as getting a bolt to push into the tube and clamp it

    You got it!  That’s it.

    // Meditation doesn't mean you have to sit still....

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