For riders seeking more performance from a 50cc scooter, upgrading to a big bore kit is a common route. A properly chosen kit can increase displacement, improve torque, and raise top speed while maintaining reliability with quality components. Below you’ll find five well-regarded options that fit Gy6 50cc to 100cc ranges, along with key considerations to help you decide which kit best meets your riding needs and maintenance preferences.
| Product | Brand | Key Feature |
|---|---|---|
| KYMLAA 100cc Big Bore Kit | KYMLAA | 69mm valve length; up to 100cc displacement; simple installation |
| Glixal 100cc Big Bore Kit with Large Valve Head | Glixal | 18.5/20.5mm valves; large valve head for more power |
| TRKIMAL 100cc Big Bore Kit | TRKIMAL | 64mm valve length; easy installation |
| Glixal 100cc 50mm Moped Kit | Glixal | Complete big bore option for GY6 100cc |
| Maoyubelt 47mm Big Bore Kit | Maoyubelt | Includes cylinder, piston, rings; power boost |
The following sections highlight five kits commonly used to upgrade 50cc scooters, focusing on compatibility, ease of installation, and potential power gains. Each product description includes practical notes to aid in decision-making for different riding styles and maintenance practices.
KYMLAA 100cc Big Bore Kit for Gy6 50cc Scooter
The KYMLAA big bore kit expands a Gy6 50cc engine to about 100cc, enabling higher RPM and stronger acceleration. It specifies a 69mm valve length version, which contributes to improved airflow and combustion efficiency when paired with the kit’s taller valve features. Installation is described as straightforward, making it suitable for riders who want noticeable gains without a complex rebuild. Pros include a potential uptick in top speed and quicker throttle response, while considerations involve ensuring compatibility with your existing CDI and exhaust setup to optimize performance.
Glixal GY6 100cc Big Bore Kit with Large Valve Head
This kit emphasizes a large valve cylinder head assembly (18.5/20.5mm) designed to boost power by improving valve flow on 139QMB/139QMA/147QMD engines found in scooters and ATVs. The 69mm long valve style head compatibility is noted, which can require mounting adjustments if your existing head uses a different valve size. A key advantage is the potential for more horsepower at higher RPMs, especially when combined with proper tuning. Ensure rocker arms are swapped if your current head uses smaller valves to avoid clearance issues.
TRKIMAL 100cc Big Bore Kit for Gy6 64mm Valve
The TRKIMAL kit targets a 64mm valve length version, offering a compatible upgrade path for riders with 64mm valve configurations. It is designed to upgrade from 50cc up to around 100cc with an emphasis on easier installation, which can be appealing for DIY enthusiasts. Pros include a balance of performance and installability, while the main consideration is valve geometry compatibility with your existing head and possibly rocker arms if your current setup differs from the kit’s specifications.
Glixal ATMT1-011 139QMB 139QMA 100cc Big Bore Kit
This Glixal kit is specifically noted for 139QMB/139QMA engines in scooters, ATVs, and go-karts. It provides a complete big bore option for 100cc displacement, which can produce meaningful power gains with appropriate supporting components (carburation, intake, exhaust). The kit’s emphasis on a proper match for the GY6 four-stroke platform makes it a popular choice among riders who own mature, well-maintained engines. Remember to verify that the kit matches your final drive and carburation configuration to maximize performance gains.
Maoyubelt 47mm Big Bore Kit for Gy6 50cc to 80cc
The Maoyubelt offering expands from 50cc toward an 80cc range with a 47mm bore, and it ships as a complete package with cylinder block, piston, rings, circlips, piston pin, head gasket set, and valve oil seals. For riders seeking a straightforward upgrade with all necessary components, this kit reduces parts sourcing hassles. The kit’s diameter and included seals require careful measurement compatibility with your engine case and head to avoid compression leaks or clearance issues during installation.
LK LEAPING KNIGHT 50mm Big Bore Head Kit
This head kit focuses on compatibility with 50cc-100cc GY6 engines, featuring a 69mm valve dimension set and a cylinder head assembly with a 69mm intake/exhaust valve arrangement. It emphasizes high performance, heat dissipation, durability, and oil efficiency. The kit’s broader valve compatibility can improve flow at higher RPMs, contributing to more robust mid-range acceleration. Ensure your engine block and head geometry align with the 69mm valve size to avoid assembly or clearance problems during installation.
ZTDZZH 50mm Bore Cylinder Head Kit
The ZTDZZH head kit is designed for 50cc to 100cc engines with a 64mm valve length, suitable for 139QA/139QMB families. It notes that the valve length is 64mm, not 69mm, which can influence port timing and intake/exhaust flow. This kit is a practical option for riders who want a dedicated head upgrade without changing the entire bottom end. As with any head-focused upgrade, compatible rocker arms and valve seals should be verified to ensure proper seating and performance.
Glixal ATMT1-008 80cc Big Bore Kit
This kit provides an 80cc option with a 47mm bore and specific cylinder dimensions. It highlights durable piston rings and a focus on reliable performance for Gy6-based scooters and go-karts. Buyers should confirm compatibility with their current engine internals, especially crankshaft and piston pin sizing, to ensure smooth operation and proper compression. The kit can offer a balanced increase in torque suitable for urban commuting and light touring when tuned appropriately.
Buying Guide
Key purchase considerations when selecting a big bore kit for a 50cc scooter include:
- Engine compatibility: Confirm engine model (e.g., Gy6 139QMB/139QMA) and valve length (64mm vs 69mm) to avoid clearance issues and improper airflow.
- Displacement and power targets: Decide whether you want a modest boost (to around 60-80cc) or a full 100cc upgrade, and factor in fuel tuning, exhaust, and CDI limitations.
- Valve and head design: Larger valve heads and higher lift can improve flow but may require rocker arm changes or different cam timing. Check if the kit includes any required oil seals or gaskets.
- Installation effort: Some kits are straightforward bolt-ons, while others require more extensive head work or carburetor adjustments. Assess your mechanical skills and available tools.
- Supporting components: Upgrades often pair with a higher-performance exhaust, air intake, and a tuned carburetor or fuel injection mapping. Ensure compatibility with your exhaust and intake setup.
- Durability and warranty: Higher displacement can stress engine components. Look for kits with quality pistons, rings, and gaskets, and review any vendor warranty terms.
- Maintenance considerations: Increased power can lead to faster wear if cooling and lubrication aren’t adequate. Plan for regular maintenance intervals and higher-quality fuel management.
- Cost versus benefit: Compare kit price, included parts, and anticipated gains against your riding needs, whether daily commuting or weekend sport riding.
- Legal and safety considerations: Ensure any modifications comply with local regulations and that the vehicle remains safe and road-legal in your area.