[How to Tutorial] Change Vacuum Lines on Hyosung GT125R GT250R & GT Comet (Air Hose Diagram)
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.
- Hyosung advises that if your factory lines are 2–4 years old, discard them regardless.
- Old pipes can rot internally, especially cheap Chinese rubber ones.
- Larger, colder air pipes can improve the vacuum system, but use strong clips!
- Strong clips are essential to prevent air leaks.
- This tutorial applies to all carb-operated 125/250 GT & GTR Twins (including GV125)
Let’s go now… strip your fairings (GTR owners)
(Naked bikes can skip this step)
Diagram of how the “AIR LINE” system should be connected:
Study the diagram images below first before moving on.
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 and follow the diagram below:
VACUUM LINE #2 = CONNECT YOUR FUEL TANK TAP
- Once the rear fuel pump is connected from the left side, move to the RIGHT side of your bike.
- Grab a second vacuum pipe and follow the diagrams below:
That’s it – Vacuum setup is done! 🚦
If you have an AIS device (Fake emissions/EGR), see below:
- Refer to the cartoon diagram of the “EGR DELETE” mod.
- Remove or block anything feeding it.
- Example image below shows setup. Personally, it’s a useless device.
- If you want it connected, replace “blocked” with “connected”.
Alright, we are done. Go test ride! 🏁
I hope this quick tutorial was easy to follow. If you get stuck or need help, just comment on this post! This also applies to GV owners since they use the same rear pump.