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

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

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

$69.99
$69.99
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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.
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Fitment FAQ

Will this part fit my specific model and year?

This cylinder piston kit is intended for This kit is a Performance Upgrade for standard 50cc 4-stroke Chinese engines.. Key physical/spec details from the product data include 13mm Piston Pin, Cylinder/Piston Bore: 47mm / 1.85", Piston Pin Size: Dia: 13mm (0.51") / Length: 37mm (1.45"). Use the compatibility table and product photos together before ordering.

Do I need to match the OEM part number?

Yes. If your original part has a stamped OEM or manufacturer number, match that number first before ordering. For this cylinder piston kit, also compare the bore diameter, piston-pin size, gasket pattern, stud spacing, engine code, stroke type, and cylinder height. This is especially important for GY6 GY6 models because similar model names can use different parts by year or trim.

What models or situations does this part not fit?

Do not order this cylinder piston kit for machines outside the listed compatibility, or for units with different bore sizes, piston-pin diameters, stroke lengths, stud spacing, or gasket patterns. Do not rely only on the model name or engine size.

What should I check before ordering?

Before ordering, compare your original part with the photos and check the bore diameter, piston-pin size, gasket pattern, stud spacing, engine code, stroke type, and cylinder height. Recheck listed specs such as 13mm Piston Pin, Cylinder/Piston Bore: 47mm / 1.85", Piston Pin Size: Dia: 13mm (0.51") / Length: 37mm (1.45"). If any connector, mounting point, size, or year detail is different, confirm fitment before installation.