Name: Carburettor Carb Air Mixture Pilot Screw x1 (CO Adjuster) - Hyosung GV125 GT125 GTR GV250 GT250
SKU: AirMixScrew2R
Availability: BackOrder

Carburettor Carb Air Mixture Pilot Screw x1 (CO Adjuster) – Hyosung GV125 GT125 GTR GV250 GT250

Estimated delivery dates: May 14, 2026 - May 15, 2026

£4.99

🛠️ MIKUNI-SPEC MIXTURE SCREW KIT

Restore factory idle and throttle response. This is the essential pilot circuit kit for Hyosung 125/250 v-twin Mikuni carbs. Often lost or damaged this kit includes the critical washer and O-ring frequently missing from old carburettors.

✅ Complete Assembly: Includes Screw, Spring, Washer, and O-ring (Item #8).
🛠️ Precision Taper: High-quality brass for accurate air/fuel metering at low RPM.
⚙️ Fixes Common Issues: Solves rough idle, popping on deceleration, and hard starts.
📦 Note: Sold individually (x1) .
Select quantity “x2” for a full twin-carb overhaul.

Tech Tip: Don’t just swap the screw—clean the pilot passage! A blocked circuit makes the best screw in the world useless.

Description

The air mixture pilot screw (CO Adjuster) is responsible for fine-tuning your idle and off-throttle fueling. On Hyosung 125/250 v-twins, these screws are often seized, snapped, or improperly assembled. We provide the full 4-piece kit to ensure your pilot circuit is sealed correctly against air leaks, which are the #1 cause of “unsolvable” rough idling.

💎 Performance with the Reliability!

This kit is more than just a screw. The inclusion of the ultra-delicate washer and O-ring is what sets it apart. These two tiny parts prevent air from bypassing the threads—a common failure point when reusing old hardware. Whether you’re fixing a snapped screw or performing a full rebuild, this is the factory-correct solution.

Full 4-Piece Kit Screw, Spring, Washer, O-ring.	Mikuni Fitment Fits front or rear carburettor.
Brass Precision Ensures smooth, accurate tuning.	Fixes Hard Starts Restores the low-end pilot circuit.

📜 Confirmed Fitment Guide (Carburettor Models Only):

This kit fits all v-twin Mikuni-style carburettors found on the following:

✅ GT125 / GT125R / GT125RC: All Carburettor Models
✅ GV125 Aquila / Mirage: All Models up to 2018
✅ GT250 / GT250R / GV250: All Carburettor Models (2005-2008)

OEM Part Numbers: 13308HG5100 // 13306HG5100 // 13307HG5100 // H13309HG5100

📖 DO IT RIGHT:
If you’re replacing this screw, your pilot jets might also be clogged. Check out our [Full Carb Tuning Tutorial] on the forums for step-by-step guidance on setting your Main Jets. Read the Carb Tuning Guide here.

🔧 Install Tips

The Critical Order: To avoid air leaks, you must install in this order: Screw ➜ Spring ➜ Washer ➜ O-Ring. The washer protects the O-ring from being chewed up by the spring!
Gentle Seating: Screw it in until it *just* touches the seat. Never force it. Over-tightening will snap the delicate brass tip inside your carb body.
Base Setting: Start at 2.5 turns out from seated as your baseline. Adjust in 1/8th turn increments while the engine is at full operating temperature.

📧 FITMENT QUESTIONS? Email us with your bike photos. For technical help on needle tuning or float heights, visit the HyoRiders Forums.