Big Bore Cylinder Rebuild Kit with 64mm Valves for 4-Stroke GY6 49cc 50cc 139QMB Racing Scooter (80cc/100cc Upgrade)

Product Overview

Unleash the hidden power of your 50cc scooter with the GOOFIT Ultimate Big Bore Kit. This "Racing Series" package is the maximum performance upgrade for GY6 50cc 139QMB engines, designed to significantly increase RPM and torque. Featuring a precision-machined cylinder and a 64mm valve head, this kit optimizes fuel combustion and enhances engine response, transforming your mild-mannered moped into a high-performance racing machine.

Product Compatibility

This kit is exclusively for the 4-stroke GY6 50cc platform. Please verify your valve length before ordering.

Category	Compatibility Details
Compatible Engines	GY6 49cc / 50cc: 139QMB, 1P39QMB
Valve Specification	64mm Valve Length Only (Does NOT fit 69mm versions)
Upgrade Purpose	Maximum RPM & Displacement Boost (80cc/100cc Class)
Vehicle Types	Racing Scooters, Mopeds, Mini Quads, Karts
Supported Brands	TaoTao, Peace Sports, Wolf, Ice Bear, Bacci, and other GY6 50cc clones

Specifications

Attribute	Technical Details & Measurements
Engine Type	4-Stroke Air-Cooled Horizontal
Valve Length	64mm (Short Valve Version)
Cylinder Type	High-Performance Big Bore
Material	Premium Alloy & High-Temp Resistant Steel
Performance Gain	Increased Top Speed & Acceleration
Kit Components	Cylinder, Head (with 64mm Valves), Piston Set, Gaskets

Key Features

• Maximum Racing Upgrade: Specifically engineered to provide the highest displacement boost possible for the 139QMB platform, ensuring more power for uphill climbs and higher top speeds.
• Optimized 64mm Valve Head: The precision-tuned cylinder head features 64mm valves that improve gas flow and prevent overheating during high-speed, high-pressure operation.
• Premium Wear Resistance: All metal components are crafted from high-grade materials, offering exceptional tolerance to heat and friction for a significantly longer engine life.
• Swifter Throttle Response: By optimizing fuel combustion efficiency, this kit delivers smoother engine operation and reduces "lag" during acceleration.
• Comprehensive Reliability: Precision machining of every core component ensures stable performance under demanding racing conditions while reducing the risk of engine failure.