How to upgrade Fuel Lines & Filter on Hyosung GT125R GT250R (Carb Hose Diagram)

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New Fuel Lines? Let’s cut to the chase… (No pun intended!)

This guide shows how to replace your stock lines with larger uprated braided ones.

Note: If your stock/original fuel lines are 2–4 years old, you must change them, as per the service manual.

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A. *️⃣ Pros & Cons of braided/fresh lines vs old stock lines

• Larger fuel filters (3× size) benefit from gravity assist & a cleaner reserve. These filters last roughly 15–20k miles (except cheap Chinese copies).
• Braided hoses last longer & are more heat-resistant than standard lines (40–100°C).
• Bigger lines allow fuel to reach the carbs faster, improving response.
• More fuel slightly improves throttle response. (Hint: Aftermarket exhausts may give a slightly deeper note.)
• If you have upgraded carb jets, larger lines help.
• Cons: None.

Be warned: Cheap Chinese fuel lines may fail within 1–2 years and risk leaks on a hot engine!

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B. 🏍 Compatible Bikes

• All carbureted GT125R & GT250R models (Carbs = large silver components between the v-twin engines)
• Naked GT Comet bikes (Unsure? Comment on this topic!)

C. 🔧 Tools Required

• Cutting tool & flat (-) screwdriver
• 10mm / 12mm spanner or socket
• Stubby / short (+) screwdriver
• Clean cloth or towel

🚧 DISCLAIMER: Work in a well-ventilated area or outdoors. Fuel vapors are flammable!
Follow this guide at your own competence. Custom parts may void warranty on new bikes! 🚧

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1. Remove the fuel tank

• Use a 10/12mm spanner or socket to remove the bolt securing the tank to the frame.
• Disconnect the 2 pipes under the tank.
• Move the tank aside. ⚠️ Watch the Fuel Level Sensor wire! Unplug carefully! ⚠️

2. Remove the Airbox

• Unscrew the bolts shown in the images below.
• 🔩 2× bolts: airbox-to-carb metal clamps (black)
• 🔩 2× bolts: airbox-to-frame

3. Bike should now look like this

4. Change the “CARB → PUMP” fuel line

• Remove the hose connecting carb to fuel pump (rear).
• Replace with new braided line.

– Keep lines straight! – – Tighten clamps to prevent leaks! –

5. Finished example: Carb to Pump

6. Ditch old filter & lines! 🚮
🚧 NOTE: Fuel may spill from old filter. ⚠️ Cover your electrics!

7. Grab your new filter & cut 2 short pipes

• Use strong clamps to prevent leaks
• Use diagram to orient the filter correctly

8. Install filter to rear pump
Keep fuel lines short & kink-free!

9. Refit Airbox

• Return to step #2 to refit airbox
• Tighten all bolts to prevent air leaks!

10. Fit the tank

• Connect final 2 pipes (fuel & air-vacuum)
• Connect Electrical Fuel Level Sensor (white plug)
• Secure tank to frame
• Tidy up & grab your helmet!

Go ride! 🏁

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Sidenotes / Q&A 🎳

1. Filter has low fuel? Check filter direction.
2. Filter looks good but still low fuel? Top-up tank.
3. High idle revs? Air leak near airbox or carburetors. Tighten all bolts & clamps.
4. Airbox is fine, still high revs? Check choke lever next to clutch lever. Slide toward front tyre to turn off.
5. Bike won’t start after fuel line change? Check pipes are connected correctly & filter is in right direction. Fuel should drip into filter on first crank.

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The end! 🎲
If you have any questions or get stuck, reply to this topic. Hope this guide helps!

Credits 📜: Images (@Danny.M) // YouTube Video (@Luke.B)