{"product_id":"naraku-qmb139-super-transmission-kit-137-1","title":"Naraku 139QMB \/ GY6 50cc Super Transmission Kit","description":"\u003cp\u003eRestore lost top speed, eliminate off-the-line bogging, and completely refresh your drivetrain with the \u003cstrong\u003eNaraku Super Transmission Kit\u003c\/strong\u003e. Engineered specifically for 50cc and 49cc GY6 50 \/ 139QMB 4-stroke engines, this all-in-one CVT tuning package replaces your entire worn factory transmission setup. By matching a high-performance variator, precision-balanced clutch assembly, heavy-duty clutch bell, and a calibrated drive belt, Naraku delivers seamless linear shifting, crisp throttle response, and maximum power transfer to the rear wheel.\u003c\/p\u003e\u003ch3\u003eWhat's Included in the Box\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003ePerformance Variator \u0026amp; Drive Face:\u003c\/strong\u003e Optimized roller ramp angles maximize belt travel for improved acceleration and high-end speed. Includes a 26-spline drive face.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePre-Assembled Clutch \u0026amp; Torque Spring Base:\u003c\/strong\u003e Features durable, high-friction clutch shoes and an anti-slip torque spring base to ensure positive engagement under load.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eHeavy-Duty Clutch Bell:\u003c\/strong\u003e Precision-vented steel clutch drum designed for rapid heat dissipation, preventing thermal glazing and clutch chatter.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePremium V-Belt:\u003c\/strong\u003e High-tensile drive belt selected for optimal dimensional stability and minimal stretching under high thermal strain.\u003c\/li\u003e\n\u003c\/ul\u003e\u003chr\u003e\u003ch3\u003eComprehensive Case Length \u0026amp; Fitment Guide\u003c\/h3\u003e\u003cp\u003eGY6 50cc engines come in three distinct case lengths. Use the drop-down menu to select the correct kit configuration for your scooter platform:\u003c\/p\u003e\u003ctable\u003e\n\u003cthead\u003e\u003ctr\u003e\n\u003cth\u003eBelt Option\u003c\/th\u003e\n\u003cth\u003eEngine Case Profile\u003c\/th\u003e\n\u003cth\u003eCommon Vehicle Applications \u0026amp; Notes\u003c\/th\u003e\n\u003c\/tr\u003e\u003c\/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003e669mm Kit\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003eShort Case (10\" Rear Wheel)\u003c\/td\u003e\n\u003ctd\u003eFits standard short-case GY6 50cc scooters running small 10-inch rear wheels (e.g., ATM50-A1, VIP, and classic city scooters).\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003e729mm Kit\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003eLong Case (12\" or 13\" Rear Wheel)\u003c\/td\u003e\n\u003ctd\u003eFits standard long-case GY6 50cc scooters running larger 12 or 13-inch wheels. Always verify your case measurement matches a long configuration.\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003e788mm Kit\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003eExtra-Long Case (Fat-Tire \/ Custom)\u003c\/td\u003e\n\u003ctd\u003eEngineered for extended-case variants, most notably found on the \u003cstrong\u003eIcebear Maddog 50cc\u003c\/strong\u003e and similar Honda Ruckus clone platforms.\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\u003eEngine Compatibility:\u003c\/strong\u003e GY6 50cc \/ 49cc 139QMB \/ QMB139 4-Stroke\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eRoller Weight Size:\u003c\/strong\u003e 16mm x 13mm (6g weights included)\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eVariator Outer Diameter:\u003c\/strong\u003e 88mm\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eDrive Face:\u003c\/strong\u003e 26 Splines | 13mm Inner Diameter | 113.7mm Outer Diameter\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eClutch Drum:\u003c\/strong\u003e 22 Splines | 11.10mm Inner Diameter\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSliding Torque Spring Base:\u003c\/strong\u003e 118mm Outer Diameter\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eManufacturer:\u003c\/strong\u003e Naraku (Germany)\u003c\/li\u003e\n\u003c\/ul\u003e\u003chr\u003e\u003cblockquote\u003e\n\u003cstrong\u003eTuning Note:\u003c\/strong\u003e The included 6g roller weights provide an excellent balanced starting point for stock or lightly modified 50cc engines. If you have an 80cc Big Bore Kit installed, experiment with heavier or lighter weights to match your modified torque curve.\u003c\/blockquote\u003e\u003cblockquote\u003e\n\u003cstrong\u003eInstallation Tip:\u003c\/strong\u003e Clean the crankshaft splines carefully before installing new components. Never use an impact gun to tighten the variator or clutch nuts without a holding tool — improper torque can strip crank threads or crush components.\u003c\/blockquote\u003e\u003chr\u003e\u003ch3\u003eAbout Naraku\u003c\/h3\u003e\u003cp\u003eNaraku is a German performance brand specializing in high-quality CVT and engine components for small-displacement scooters and mopeds. Known for tight manufacturing tolerances and rigorous quality control, Naraku parts are a trusted upgrade over OEM for riders who demand more from their 50cc platform.\u003c\/p\u003e\u003chr\u003e\u003cp\u003e\u003cstrong\u003eSKU:\u003c\/strong\u003e 137-1  |  \u003cstrong\u003eVendor:\u003c\/strong\u003e Naraku  |  \u003cstrong\u003eCategory:\u003c\/strong\u003e Engine \u0026amp; Transmission \/ Complete CVT Kits\u003c\/p\u003e\u003cp\u003e\u003ca href=\"https:\/\/www.p65warnings.ca.gov\" target=\"_blank\"\u003eCalifornia Prop 65 Warning: www.p65warnings.ca.gov\u003c\/a\u003e\u003c\/p\u003e","brand":"Naraku","offers":[{"title":"Default Title","offer_id":48112268574907,"sku":"137-1     788","price":278.0,"currency_code":"USD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0719\/1340\/6651\/files\/137-1.webp?v=1784307242","url":"https:\/\/thriftyscooters.com\/products\/naraku-qmb139-super-transmission-kit-137-1","provider":"Thrifty Scooters","version":"1.0","type":"link"}