Prima 4mm Main Jet Tuning Kit - Keihin PB & CVK Carburetors

Fine-Tune Your Fuel: 10-Piece Prima 4mm Main Jet Kit Standard factory jetting is almost always "lean" to meet emissions standards, which can leave your scooter feeling sluggish. The Prima 4mm Main Jet Kit is the essential tool for riders installing big-bore kits, performance exhausts, or high-flow air filters. With 10 precision-machined sizes, you can eliminate "flat spots" and find the perfect air-fuel ratio for maximum throttle response. The Tuner’s Advantage Complete Range: Includes 10 sizes (#70, #75, #80, #85, #90, #95, #100, #105, #110, #115) to cover everything from stock to fully-modified builds. Precision Machined: Every jet is stamped with its size and built to strict tolerances, ensuring consistent fuel flow across the entire RPM range. Universal 4mm Thread: Specifically designed for Keihin PB, CVK, and PD18J carburetors commonly found on 50cc–125cc scooters. Value Bundle: Buying a kit is 60% more cost-effective than purchasing individual jets during the trial-and-error tuning process. Comprehensive Fitment Guide This 4mm kit fits most 50cc to 125cc "retro" and performance scooters using a 139QMB engine or Genuine 2-stroke platforms: Brand Compatible Models Genuine Scooter Co. Buddy 50, Roughhouse 50, Black Jack 50, Buddy 125 Kymco Agility 50, Super 8 50, People 50 (4-Stroke) SYM Orbit 50, Fiddle II 50, Jet 50 CSC / Wolf / Amigo Bella Classic, Lucky, Avenza, and most 139QMB builds Honda Metropolitan (CHF50), Ruckus (NPS50) - *Check thread first* Technical Specifications Thread Size: M4 x 0.7mm Jet Body Diameter: 5mm Overall Length: 7mm Material: High-Grade Brass SKU: 114-49-10PCS Pro Tuning Tip: Always start with the largest jet first and work your way down. A "rich" mixture (too much fuel) is safe, but a "lean" mixture (too little fuel) can cause your engine to overheat and seize. Look for a "toasted marshmallow" brown color on your spark plug for the perfect tune. Note: Not compatible with Mikuni or Dellorto carburetors. Please verify that your current jet has an M4 thread before ordering. Original Parts For Scooters SKU 114-49-10PCS, 114-85-10PCS