YCF Size 38 Slow Jet for Nibbi Carburetors on Select YCF Dirt Bikes (2024-2025)

Fine-tune your dirt bike’s performance with this YCF Size 38 Slow Jet made for Nibbi Carburetors. This slow-jet is designed for riders who demand smooth throttle response and reliable low-speed fueling, this precision-machined brass jet fits select YCF dirt bikes equipped with Nibbi carburetors (2024-2025).

This size 38 slow jet, also known as a pilot jet, controls the fuel mixture at idle and low-throttle openings, ensuring crisp response and stable engine performance. Manufactured to Nibbi specifications, it delivers consistent flow characteristics that help prevent bogging, hesitation, or stalling in off-idle conditions.

This jet is compatible with Nibbi carburetors that use PE and PWK main jets, allowing versatile fitment across YCF bike models. Whether you’re replacing a worn jet or dialing in your fuel system after altitude or exhaust changes, this slow jet provides the accuracy and quality your bike deserves.

Features & Benefits

• Size 38 jet for stable idle and smooth low-throttle control
• Compatible with both PE and PWK main jets for versatile tuning options
• Precision-machined brass ensures consistent fuel flow
• Designed to improve throttle response and prevent lean hesitation
• Reliable for performance for track, trail, and everyday riding
• Durable finish provides corrosion resistance from fuel exposure

What's Included

• (1) YCF Size 38 Slow Jet for Nibbi Carburetors on Select YCF Dirt Bikes (2024-2025)

Fitment

• START 125SE (2024–2025)
•  START 125S (2024)
•  START 125 (2024–2025)
•  PILOT 125 (2024–2025)
•  PILOT 150E (2024–2025)
•  FACTORY SP2 150 (2024–2025)
•  BIGY 125 (2024–2025)
•  BIGY 150 (2024–2025)
•  BIGY 150E FACTORY (2024)
•  BIGY 150E FACTORY XL (2024–2025)
•  LITE 125 (2024–2025)
•  SM 125 (2024–2025)
•  SM 155 (2024–2025)
•  SUNDAY S124E (2025)
•  SUNDAY S147E (2025)
•  GP 107A (2024)
•  GP 157 (2025)

Specifications

• Material: Brass
• Function: Controls fuel & air mixture while engine is idling 
• Dimensions: M6 x 0.75mm thread size, 1" (28mm) length, 5mm head diameter
• Application: MX, enduro, track, trial, pit bike

FAQ - Common Buyer Questions

Q: What does a "slow jet" do in a carburetor?

A: The slow (pilot) jet controls fuel delivery at idle and low throttle openings, crucial for maintaining smooth idle, clean starts, and steady low-speed response.

Q: Do I need to re-tune my carburetor after installation?

A: Minor fuel-screw or idle-speed adjustments may be needed to optimize your bike's performance, depending o conditions such as temperature, altitude, and exhaust setup. 

Q: Can I use this jet for racing or recreational riding?

A: Absolutely. The precise metering supports consistent throttle response for both competition and everyday use.