For riders seeking more power from a 50cc scooter, the biggest big bore kits can push displacement toward 100cc. This guide compares five top Gy6-based upgrades and a select 80cc option, highlighting performance gains, valve length differences, and installation considerations.
Below is a concise table of the five selected kits with brand and notable specs to help readers compare at a glance.
| Product | Brand | Displacement (cc) | Notes |
|---|---|---|---|
| TRKIMAL 100cc Gy6 Big Bore Kit | TRKIMAL | 100 | 64mm valve length; no EGR; easy installation; includes 6-pin CDI, ignition coil, spark plug, clutch spring |
| KYMLAA 100cc Gy6 Big Bore Kit | KYMLAA | 100 | 69mm valve length; simple installation; includes racing CDI and ignition components |
| TRKIMAL 100cc Big Bore Kit With 69mm Valve | TRKIMAL | 100 | Cylinder body kit, head kit, camshaft set, gaskets, oil pump, gears, spring sets; 6-pin CDI and ignition coil |
| Maoyubelt 47mm Big Bore Kit (80cc) | Maoyubelt | 80 | Includes cylinder block, piston, rings, clips, piston pin, head gasket set, valve seals; 47mm bore |
| XMT-MOTO 80cc Big Bore Kit | XMT-MOTO | 80 | Aluminum alloy; compatible with multiple 49cc–50cc four-stroke scooters; aftermarket kit |
Product 1
The TRKIMAL 100cc Gy6 Big Bore Kit raises displacement from typical 50cc configurations to 100cc by using a 64mm valve-length version. It is designed for Gy6 platforms including 49cc, 50cc, and 139QMB mopeds and scooters, delivering higher RPM, more power, and a faster top speed. The package emphasizes easy installation and does not require EGR modifications. It also includes performance components such as a 6-pin racing CDI, ignition coil, a high-performance spark plug, and a clutch spring to support higher RPM operation, helping the engine respond more readily at higher speeds.
Product 2
The KYMLAA 100cc Big Bore Kit for Gy6 engines uses a 69mm valve-length version to push power toward 100cc while maintaining a straightforward installation. Designed for 50cc, 60cc, and 80cc Gy6 platforms, this kit aims to increase RPM and top speed without demanding extensive modification. It includes essential performance electronics, such as a 6-pin racing CDI and ignition coil, plus a high-performance spark plug and clutch spring, to help the engine run reliably at higher RPM ranges. The kit targets riders seeking a more responsive scooter without sacrificing ease of use.
Product 3
TRKIMAL’s 100cc Big Bore Kit With 69mm Valve expands a Gy6 50cc/60cc/80cc engine toward 100cc. It provides a complete upgrade path, including cylinder body kits, head kits, camshaft assemblies, gasket sets, oil pump and gear, spring sets, and copper roller sets. The package also includes a racing AC CDI, an ignition coil, and a racing three-electrode spark plug. With a 69mm valve-length version, this kit emphasizes comprehensive components for a robust upgrade, designed for vehicles like 49cc and 50cc Gy6 engines and their related 139QMB variants.
Product 4
Maoyubelt’s 47mm Big Bore Kit is designed to upgrade Gy6 engines from 50cc up to 80cc. The kit is sold as a complete package, including a cylinder block, piston, complete ring set, circlips, piston pin, head gasket set, and valve oil seals. The bore is specified at 47mm, with additional dimensional notes indicating a 53.2mm range variant. This kit targets owners looking for a sizeable displacement increase with a full component set to support a reliable upgrade, helping to unlock more torque and greater acceleration on compatible scooters.
Product 5
XMT-MOTO’s 80cc Big Bore Kit for Gy6 scooters uses an aluminum bore kit designed for compatibility with a wide range of 49cc–50cc four-stroke scooters. The kit is described as 100% brand new aftermarket and emphasizes aluminum construction to balance weight and heat dissipation. It supports popular models such as Roketa, Taotao, Baja Silver, and numerous other 49cc–50cc platforms. This option focuses on maximizing displacement while aiming to preserve reliability and fitment across multiple scooter configurations, making it a versatile choice for riders seeking moderate, dependable gains without extensive reworking of the engine bay.
Buying Guide
Choosing a big bore kit for a 50cc scooter involves balancing displacement gains with reliability, compatibility, and maintenance demands. Below are essential considerations to help buyers compare options and select the right kit for their setup.
Compatibility And Fitment
Verify your scooter’s engine type and model (for example, Gy6, 139QMB/139QMA, Roketa, Taotao, etc.). Some kits target four-stroke Gy6 engines, while others are suitable for two-stroke Yamaha Jog or clones. Valve-length compatibility (64mm vs 69mm) can affect clearance with valves, camshafts, and spark plugs. Check bore size and stroke to ensure the piston assembly will fit within the cylinder head and exhaust without interference. If your scooter uses a specific crankshaft or cam setup, confirm the kit’s components align with your model’s specifications.
Displacement, Performance, And Longevity
100cc kits generally deliver the most noticeable gains in torque and top speed, but not all 100cc configurations are equal. Bore size, valve length, and the inclusion of supporting parts (cam, oil pump, gaskets) influence performance and durability. An 80cc option can offer a solid balance of power and reliability for daily riders. Consider whether you will upgrade cooling, carburetion, and ignition timing, and be prepared for changes in fuel economy and maintenance intervals as displacement increases.
Quality Of Materials And Components
Look for high-quality aluminum cylinders, robust piston rings, and durable gaskets. Some kits include electronics such as racing CDI units and ignition coils; these can improve performance at higher RPMs but may require tuning. A comprehensive kit with gaskets, seals, and timing components reduces the number of additional purchases needed. Evaluate the reputation of the brand and any available documentation or setup guides to gauge long-term reliability.
Installation Requirements
Big bore upgrades often require more than a new cylinder. You may need a new head gasket set, oil pump or gear, camshaft components, and sometimes a new carburetor or air intake tuning. Have a plan for installation, including tools, torque specs, and potential engine breathing adjustments (jetting and air-fuel mixture). If you’re less confident with mechanical work, choosing a kit that includes more components and clear instructions can simplify the project.
Cooling, Fuel, And Tuning
Higher displacement increases heat output. Ensure your cooling system is in good condition and consider upgrading cooling if necessary. Jetting and fuel delivery may require adjustment to avoid running lean or rich conditions at higher RPM. If your kit includes a racing CDI or ignition upgrade, verify compatibility with your spark timing and ignition system to prevent premature wear or engine knock.
Warranty, Support, And Legal Considerations
Check warranty terms and available after-sales support. Some kits come with extensive documentation and community forums that help with installation and troubleshooting. Be aware of local regulations regarding engine, emissions, and licensing; large bore upgrades can affect warranty coverage, insurance, and legality in certain areas. Regular maintenance after installation is essential to preserve longevity and performance gains.
Choosing The Right Kit For Your Scooter
For maximum performance with solid reliability, prioritize kits that provide complete component sets and documented compatibility with your scooter model. If you aim for the highest airflow and top speed, a 100cc kit with a compatible valve length and reliable CDI/ignition components is appealing, provided cooling and fueling are addressed. If ease of installation is critical, select a kit marketed as “easy installation” with included gaskets, seals, and a straightforward instruction set. Always ensure the engine’s cooling, ignition timing, and fuel system are prepared for higher RPMs to maintain engine health over time.