{"product_id":"universal-parts-qmb139-cylinder-head-kit-64mm-valves-151-242","title":"Universal Parts QMB139 Cylinder \u0026 Head Kit | 39\/47\/50mm","description":"Complete cylinder and head kit for QMB139 4-stroke 50cc engines. Choose from 39mm (stock), 47mm (72cc upgrade), or 50mm (81.3cc upgrade) bore from the drop-down. Includes everything needed for a full top-end rebuild. Note: larger bore sizes may require engine case modification.\u003cstrong\u003eKit includes:\u003c\/strong\u003e complete cylinder head, cylinder, piston, rings, piston pin, circlips, head gasket, and base gasket.\u003cul\u003e\n\u003cli\u003eCylinder bore: 39mm (stock) \/ 47mm (72cc) \/ 50mm (81.3cc) — select at checkout\u003c\/li\u003e\n\u003cli\u003eCylinder sleeve OD: 45mm (39mm bore) \/ 52.8mm (47mm bore) \/ 53.95mm (50mm bore)\u003c\/li\u003e\n\u003cli\u003eWrist pin diameter: 13mm\u003c\/li\u003e\n\u003cli\u003eTotal piston height: 34.4mm\u003c\/li\u003e\n\u003cli\u003eCompression height (wrist pin center to piston top): 17.25mm\u003c\/li\u003e\n\u003cli\u003eIntake and exhaust valve length: 64mm\u003c\/li\u003e\n\u003cli\u003eNon-emissions head\u003c\/li\u003e\n\u003cli\u003eWeight: 4.75–5 lbs (varies by bore)\u003c\/li\u003e\n\u003c\/ul\u003e\u003cstrong\u003eCompatible Engine:\u003c\/strong\u003e\u003cul\u003e\n\u003cli\u003eQMB139 (139QMB) 49cc \/ 50cc 4-stroke\u003c\/li\u003e\n\u003cli\u003eGenuine Buddy 50, RoughHouse 50, Rattler 50, and other QMB139-powered scooters\u003c\/li\u003e\n\u003c\/ul\u003e\u003cstrong\u003eNote:\u003c\/strong\u003e Larger bore sizes (47mm and 50mm) may require modification to the engine case to accommodate the larger cylinder.\u003cstrong\u003eFor off-road and closed-course competition use only. Not intended for use on public roads.\u003c\/strong\u003e\u003ca href=\"http:\/\/www.p65warnings.ca.gov\"\u003eCalifornia Prop 65 Warning: www.p65warnings.ca.gov\u003c\/a\u003e","brand":"Universal Parts","offers":[{"title":"Default Title","offer_id":48112317726907,"sku":"151-242   50","price":84.0,"currency_code":"USD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0719\/1340\/6651\/files\/151-242.webp?v=1784310463","url":"https:\/\/thriftyscooters.com\/products\/universal-parts-qmb139-cylinder-head-kit-64mm-valves-151-242","provider":"Thrifty Scooters","version":"1.0","type":"link"}