{"product_id":"gy6s-169-239-ssp-g-44mm-stroker-crankshaft-assembly-for-50cc-4-stroke-qmb139-engines","title":"SSP-G 44mm STROKER CRANKSHAFT ASSEMBLY FOR 50cc 4-STROKE QMB139 ENGINES","description":"44mm Stroker Crankshaft Assembly for 50cc GY6 \/ QMB139 4-Stroke Engines \u003cp\u003eIncrease the displacement and performance of your 50cc GY6 QMB139 engine with this \u003cstrong\u003e44mm Performance Stroker Crankshaft Assembly\u003c\/strong\u003e. Designed for serious engine builders, this crankshaft increases stroke over the factory crank, allowing your engine to produce significantly more torque and horsepower when paired with the proper big bore cylinder kit.\u003c\/p\u003e \u003cp\u003eManufactured from high-strength steel with a precision-balanced crank assembly, this stroker crank is built to withstand higher RPMs while delivering smooth, reliable performance for both street and racing applications. It is an excellent upgrade for 72cc, 80cc, 90cc, and 100cc performance engine builds utilizing the QMB139 platform. The 44mm stroke is approximately 2.6mm longer than the stock crankshaft, increasing engine displacement and improving low-end torque and acceleration. \u003c\/p\u003e \u003ch2\u003eSpecifications\u003c\/h2\u003e \u003cul\u003e \u003cli\u003eEngine Type: GY6 50cc \/ QMB139 4-Stroke\u003c\/li\u003e \u003cli\u003eStroke: \u003cstrong\u003e44mm Performance Stroker\u003c\/strong\u003e\n\u003c\/li\u003e \u003cli\u003eOverall Length: \u003cstrong\u003e247mm\u003c\/strong\u003e\n\u003c\/li\u003e \u003cli\u003eThread Size (Tapered Side): \u003cstrong\u003eM10 x 1.25\u003c\/strong\u003e\n\u003c\/li\u003e \u003cli\u003eThread Size (Spline Side): \u003cstrong\u003eM12 x 1.25\u003c\/strong\u003e\n\u003c\/li\u003e \u003cli\u003eBearing Outside Diameter (Magneto Side): \u003cstrong\u003e42mm\u003c\/strong\u003e\n\u003c\/li\u003e \u003cli\u003eBearing Outside Diameter (CVT Side): \u003cstrong\u003e47mm\u003c\/strong\u003e\n\u003c\/li\u003e \u003cli\u003eNumber of Splines: \u003cstrong\u003e26\u003c\/strong\u003e\n\u003c\/li\u003e \u003cli\u003eConnecting Rod Small End (Wrist Pin): \u003cstrong\u003e13mm\u003c\/strong\u003e\n\u003c\/li\u003e \u003cli\u003eOil Pump Drive Gear: \u003cstrong\u003e16 Teeth\u003c\/strong\u003e\n\u003c\/li\u003e \u003cli\u003eRequired Oil Pump: \u003cstrong\u003e33-Tooth Oil Pump\u003c\/strong\u003e\n\u003c\/li\u003e \u003cli\u003ePrecision Balanced Assembly\u003c\/li\u003e \u003cli\u003eHigh-Strength Forged Steel Connecting Rod\u003c\/li\u003e \u003cli\u003eHeavy-Duty Crank Pin\u003c\/li\u003e \u003cli\u003eHigh-RPM Performance Design\u003c\/li\u003e \u003c\/ul\u003e \u003ch2\u003ePerformance Benefits\u003c\/h2\u003e \u003cul\u003e \u003cli\u003eIncreases engine displacement\u003c\/li\u003e \u003cli\u003eProduces more low-end torque\u003c\/li\u003e \u003cli\u003eStronger acceleration\u003c\/li\u003e \u003cli\u003eBetter hill-climbing performance\u003c\/li\u003e \u003cli\u003eImproves throttle response\u003c\/li\u003e \u003cli\u003eHigher horsepower potential\u003c\/li\u003e \u003cli\u003eSmooth operation at elevated RPM\u003c\/li\u003e \u003cli\u003eIdeal foundation for high-performance engine builds\u003c\/li\u003e \u003cli\u003ePrecision-balanced to reduce vibration\u003c\/li\u003e \u003cli\u003eDurable construction for long service life\u003c\/li\u003e \u003c\/ul\u003e \u003ch2\u003eRecommended Engine Builds\u003c\/h2\u003e \u003cp\u003eThis crankshaft is commonly used with:\u003c\/p\u003e \u003cul\u003e \u003cli\u003e47mm (72cc) Big Bore Kits\u003c\/li\u003e \u003cli\u003e50mm (90cc) Big Bore Kits\u003c\/li\u003e \u003cli\u003e52.4mm (100cc) Big Bore Kits\u003c\/li\u003e \u003cli\u003ePerformance camshafts\u003c\/li\u003e \u003cli\u003eHigh-compression cylinder heads\u003c\/li\u003e \u003cli\u003ePerformance CDI units\u003c\/li\u003e \u003cli\u003e19mm–24mm carburetors\u003c\/li\u003e \u003cli\u003eRacing variators\u003c\/li\u003e \u003cli\u003eLightweight roller or slider weights\u003c\/li\u003e \u003cli\u003ePerformance clutch assemblies\u003c\/li\u003e \u003cli\u003eFree-flow performance exhaust systems\u003c\/li\u003e \u003c\/ul\u003e \u003ch2\u003eCompatible Engines\u003c\/h2\u003e \u003cp\u003eFits most Chinese-built 50cc 4-stroke engines including:\u003c\/p\u003e \u003cul\u003e \u003cli\u003eGY6 50cc\u003c\/li\u003e \u003cli\u003eQMB139\u003c\/li\u003e \u003cli\u003e139QMB\u003c\/li\u003e \u003cli\u003e139QMA\u003c\/li\u003e \u003c\/ul\u003e \u003ch2\u003eCommon Vehicle Fitment\u003c\/h2\u003e \u003cp\u003eCompatible with many Chinese scooters using the QMB139 engine, including numerous models from:\u003c\/p\u003e \u003cul\u003e \u003cli\u003eTaoTao\u003c\/li\u003e \u003cli\u003eRoketa\u003c\/li\u003e \u003cli\u003eJonway\u003c\/li\u003e \u003cli\u003ePeace Sports\u003c\/li\u003e \u003cli\u003eBMS\u003c\/li\u003e \u003cli\u003eIce Bear\u003c\/li\u003e \u003cli\u003eWolf Brand Scooters\u003c\/li\u003e \u003cli\u003eTank Sports\u003c\/li\u003e \u003cli\u003eSUNL\u003c\/li\u003e \u003cli\u003eLance\u003c\/li\u003e \u003cli\u003eZnen\u003c\/li\u003e \u003cli\u003eJMStar\u003c\/li\u003e \u003cli\u003eBaja\u003c\/li\u003e \u003cli\u003eEagle\u003c\/li\u003e \u003cli\u003eDongfang\u003c\/li\u003e \u003cli\u003eVento\u003c\/li\u003e \u003cli\u003eCoolster (QMB139-equipped scooters)\u003c\/li\u003e \u003cli\u003eYerf-Dog scooters equipped with QMB139 engines\u003c\/li\u003e \u003c\/ul\u003e \u003cp\u003e\u003cstrong\u003eAlways verify engine code, crankshaft dimensions, bearing sizes, and oil pump gear compatibility before purchasing.\u003c\/strong\u003e\u003c\/p\u003e \u003ch2\u003eInstallation Notes\u003c\/h2\u003e \u003cul\u003e \u003cli\u003e\n\u003cstrong\u003eRequires a 33-tooth oil pump\u003c\/strong\u003e due to the integrated 16-tooth crankshaft drive gear.\u003c\/li\u003e \u003cli\u003eNew crankshaft bearings and seals are highly recommended during installation.\u003c\/li\u003e \u003cli\u003eCrankcase machining may be required for certain large-displacement engine combinations.\u003c\/li\u003e \u003cli\u003eProper crankshaft alignment and professional installation are recommended for maximum reliability.\u003c\/li\u003e \u003cli\u003eAlways check piston-to-valve and piston-to-head clearance when using stroker crankshafts with aftermarket cylinder kits.\u003c\/li\u003e \u003cli\u003ePairing this crank with a quality big bore kit and properly tuned CVT will provide the best performance gains.\u003c\/li\u003e \u003c\/ul\u003e \u003ch2\u003eWhy Upgrade to a 44mm Stroker Crank?\u003c\/h2\u003e \u003cp\u003eUnlike a standard replacement crankshaft, a 44mm stroker crank increases piston travel, creating a larger engine displacement without sacrificing reliability. The longer stroke improves cylinder filling, resulting in stronger torque throughout the RPM range, quicker acceleration, and increased horsepower when combined with supporting performance components. It is one of the most popular upgrades for riders building dependable high-performance QMB139 engines. \u003c\/p\u003e","brand":"ChinesePartsPro","offers":[{"title":"Default Title","offer_id":53556338164024,"sku":"169-239","price":122.5,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0011\/8898\/6997\/files\/DSCN6256__49572.1782935957.jpg?v=1792867231","url":"https:\/\/www.chinesepartspro.com\/products\/gy6s-169-239-ssp-g-44mm-stroker-crankshaft-assembly-for-50cc-4-stroke-qmb139-engines","provider":"ChinesePartsPro","version":"1.0","type":"link"}