{"product_id":"prima-keihin-pb-main-jet-kit-4mm-10-pcs-qmb139-gen-50cc-1300-1129","title":"Prima 4mm Main Jet Tuning Kit - Keihin PB \u0026 CVK Carburetors","description":"\u003ch2\u003eFine-Tune Your Fuel: 10-Piece Prima 4mm Main Jet Kit\u003c\/h2\u003e\u003cp\u003eStandard factory jetting is almost always \"lean\" to meet emissions standards, which can leave your scooter feeling sluggish. The \u003cstrong\u003ePrima 4mm Main Jet Kit\u003c\/strong\u003e 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.\u003c\/p\u003e\u003ch3\u003eThe Tuner’s Advantage\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eComplete Range:\u003c\/strong\u003e Includes 10 sizes (#70, #75, #80, #85, #90, #95, #100, #105, #110, #115) to cover everything from stock to fully-modified builds.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePrecision Machined:\u003c\/strong\u003e Every jet is stamped with its size and built to strict tolerances, ensuring consistent fuel flow across the entire RPM range.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eUniversal 4mm Thread:\u003c\/strong\u003e Specifically designed for \u003cstrong\u003eKeihin PB, CVK, and PD18J\u003c\/strong\u003e carburetors commonly found on 50cc–125cc scooters.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eValue Bundle:\u003c\/strong\u003e Buying a kit is 60% more cost-effective than purchasing individual jets during the trial-and-error tuning process.\u003c\/li\u003e\n\u003c\/ul\u003e\u003chr\u003e\u003ch3\u003eComprehensive Fitment Guide\u003c\/h3\u003e\u003cp\u003eThis 4mm kit fits most 50cc to 125cc \"retro\" and performance scooters using a 139QMB engine or Genuine 2-stroke platforms:\u003c\/p\u003e\u003ctable style=\"width: 100%; border-collapse: collapse;\"\u003e\n\u003cthead\u003e\u003ctr style=\"background-color: #f2f2f2;\"\u003e\n\u003cth style=\"padding: 8px; border: 1px solid #ddd;\"\u003eBrand\u003c\/th\u003e\n\u003cth style=\"padding: 8px; border: 1px solid #ddd;\"\u003eCompatible Models\u003c\/th\u003e\n\u003c\/tr\u003e\u003c\/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding: 8px; border: 1px solid #ddd;\"\u003e\u003cstrong\u003eGenuine Scooter Co.\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd style=\"padding: 8px; border: 1px solid #ddd;\"\u003eBuddy 50, Roughhouse 50, Black Jack 50, Buddy 125\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding: 8px; border: 1px solid #ddd;\"\u003e\u003cstrong\u003eKymco\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd style=\"padding: 8px; border: 1px solid #ddd;\"\u003eAgility 50, Super 8 50, People 50 (4-Stroke)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding: 8px; border: 1px solid #ddd;\"\u003e\u003cstrong\u003eSYM\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd style=\"padding: 8px; border: 1px solid #ddd;\"\u003eOrbit 50, Fiddle II 50, Jet 50\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding: 8px; border: 1px solid #ddd;\"\u003e\u003cstrong\u003eCSC \/ Wolf \/ Amigo\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd style=\"padding: 8px; border: 1px solid #ddd;\"\u003eBella Classic, Lucky, Avenza, and most 139QMB builds\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding: 8px; border: 1px solid #ddd;\"\u003e\u003cstrong\u003eHonda\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd style=\"padding: 8px; border: 1px solid #ddd;\"\u003eMetropolitan (CHF50), Ruckus (NPS50) - *Check thread first*\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\u003chr\u003e\u003ch3\u003eTechnical Specifications\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eThread Size:\u003c\/strong\u003e M4 x 0.7mm\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eJet Body Diameter:\u003c\/strong\u003e 5mm\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eOverall Length:\u003c\/strong\u003e 7mm\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMaterial:\u003c\/strong\u003e High-Grade Brass\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSKU:\u003c\/strong\u003e 114-49-10PCS\u003c\/li\u003e\n\u003c\/ul\u003e\u003chr\u003e\u003cblockquote\u003e\n\u003cstrong\u003ePro Tuning Tip:\u003c\/strong\u003e Always start with the \u003cstrong\u003elargest jet first\u003c\/strong\u003e 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.\u003c\/blockquote\u003e\u003cp style=\"font-size: 0.85em; color: #666;\"\u003e\u003cstrong\u003eNote:\u003c\/strong\u003e Not compatible with Mikuni or Dellorto carburetors. Please verify that your current jet has an M4 thread before ordering.\u003cb data-path-to-node=\"2,0\" data-index-in-node=\"0\"\u003e\u003c\/b\u003e\u003c\/p\u003e\u003cp\u003eOriginal Parts For Scooters SKU 114-49-10PCS, 114-85-10PCS\u003c\/p\u003e\u003cp class=\"MsoNormal\" style=\"margin-bottom: 0in;\"\u003e \u003c\/p\u003e","brand":"Prima","offers":[{"title":"Default Title","offer_id":46760606040344,"sku":"1300-1129","price":19.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0782\/1728\/1816\/products\/1300-1129_91e13573-4cf8-43e9-8cc6-36535b480cf2.jpg?v=1772579446","url":"https:\/\/www.scooterworks.com\/products\/prima-keihin-pb-main-jet-kit-4mm-10-pcs-qmb139-gen-50cc-1300-1129","provider":"Scooterworks USA, LLC","version":"1.0","type":"link"}