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

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.

📜 Confirmed Fitment Guide (Carburettor Models Only):

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

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

🔧 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.