47mm Big Bore Cylinder Rebuild Kit (80cc Upgrade) for GY6 50cc 139QMB 139QMA 4-Stroke Scooter ATV (Non-EGR)

Product Overview

Upgrade your GY6 50cc engine to a high-performance 80cc powerhouse with the GOOFIT 47mm Big Bore Kit. This comprehensive rebuild set is designed to increase displacement, providing a significant boost in torque and acceleration for your scooter, ATV, or go-kart. Specifically engineered for Non-EGR 139QMB/139QMA engines, this kit includes everything from the cylinder head to the A7TC spark plug, ensuring a total top-end transformation for maximum reliability.

Product Compatibility

This kit is a Performance Upgrade for standard 50cc 4-stroke Chinese engines.

⚠️ NOTE: This is a Non-EGR cylinder head. Please check your original engine to ensure it does not require an EGR (Exhaust Gas Recirculation) port.

Engine Platform	Displacement Upgrade	Fitment Type
GY6 50cc (139QMB)	Upgrades to 80cc	Non-EGR Systems
GY6 50cc (139QMA)	Upgrades to 80cc	13mm Piston Pin
Compatible Vehicles	TaoTao, Wolf, Ice Bear, Bacci	Most 4-Stroke Scooters

Specifications

Attribute	Details
Cylinder/Piston Bore	47mm / 1.85"
Piston Pin Size	Dia: 13mm (0.51") / Length: 37mm (1.45")
Valves Size	Intake: 20mm (0.78") / Exhaust: 30mm (1.18")
Mounting Spacing	45mm (Intake) / 50mm (Exhaust)
Spark Plug Included	A7TC
Engine Type	4-Stroke (Non-EGR)

Key Features

• Instant 80cc Displacement Boost: Converts your regular 50cc engine into an 80cc performance motor, delivering noticeable improvements in climbing power and top speed.
• Non-EGR Optimized Design: Features a high-hardness cylinder head without EGR ports, reducing air leakage risks and simplifying the installation for standard 139QMB platforms.
• Premium Friction Reduction: The precision-honed cylinder bore and 47mm piston are designed to minimize friction, ensuring a cooler-running engine and smoother power delivery.
• Durable & Corrosion Resistant: Constructed from high-grade, rustproof alloys that withstand high thermal stress, providing a long service life even under frequent high-load operation.
• All-in-One Rebuild Kit: Comes complete with the cylinder head, piston assembly, rings, 13mm pin, gaskets, and spark plug—everything needed to replace your old or broken top-end.