Upgrading a pit bike with a big bore kit can boost displacement, torque, and throttle response, turning a stock ride into a more competitive machine. This guide highlights five reputable big bore kits designed for common pit bike engines in the 110cc–140cc range and beyond. Each kit includes essential components and is chosen for compatibility with popular Chinese and YinXiang engine families. Compare bore sizes, included parts, and installation notes to pick the kit that best fits your bike and riding style.
| Product | Brand | Bore Size | Compatibility |
|---|---|---|---|
| PowerMotor 56mm Big Bore Kit | PowerMotor | 56 mm | YINXIANG 140cc and similar 1P56 engines |
| HANQIMOTO YX140 56mm Kit | HANQIMOTO | 56 mm | YX 140cc/150cc family, 1P56 versions |
| FLYPIG 52.4mm Big Bore Kit | FLYPIG | 52.4 mm | Most 110cc Chinese engines (ATV, dirt bike, pit bike) |
| TRKIMAL 52.4mm Big Bore Kit | TRKIMAL | 52.4 mm | Various 110cc Chinese four-stroke engines |
| JooWing 250CC Big Bore Kit | JooWing | 67 mm | 250cc air-cooled engines (ATV, quad, go kart, dirt bike) |
PowerMotor 56mm Big Bore Kit
The PowerMotor 56mm Kit is designed as a direct upgrade for 56mm bore YinXiang 140cc horizontal engines and similar 1P56 family units. The kit’s inner diameter is 56mm with a 145mm cylinder length and a 100mm height, delivering a noticeable increase in displacement and power over stock configurations. Included components cover the essential top-end upgrade: a 56mm bore cylinder plus piston ring gasket kit. This package is aimed at riders seeking reliable, drop-in replacement parts without extensive modification.
- 56mm bore cylinder
- Includes piston ring gasket kit
- Compatible with YinXiang 140cc horizontal engines and related models
- Precisely sized for straightforward top-end work
Installation considerations include confirming cylinder and head compatibility with your specific 1P56FMJ W063 or related variants, verifying space for the 145mm cylinder length, and ensuring proper gasket seating to prevent loss of compression. The kit is best suited for riders who want a reliable, factory-style upgrade without sourcing multiple separate components.
HANQIMOTO YX140 56mm Kit
The HANQIMOTO 56mm YX140 kit targets a broad range of 1P56 systems, including W063 variants and related 140cc/150cc platforms. It comes as a top-end rebuild kit with a cylinder, piston kit, piston ring set, gasket kit, and a spark plug, enabling a complete top-end refresh. The kit emphasizes compatibility with popular pit bike and go-kart models from KAYO, BSE, Xmotos, Apollo, Orion, SSR, and others in the same family, helping riders extend engine life and improve thermals with a single purchase.
- 56mm bore suitable for 140cc/150cc engines
- Includes cylinder, piston kit, rings, gasket kit, spark plug
- Top-end rebuild focus for mix of brands (KAYO/BSE/Xmotos/SSR, etc.)
Practical considerations include verifying exact model compatibility via the description, ensuring the top-end rebuild kit matches your engine’s head and cooling configuration, and planning for proper torque specs during reassembly. This kit is ideal for owners who want a complete upgrade packaged for reliable, long-term operation.
FLYPIG 52.4mm Big Bore Kit
The FLYPIG 52.4mm kit targets the majority of 110cc Chinese engines, including ATV, dirt bike, pit bike, go-kart, and pocket bikes. It provides a 52.4mm bore option designed to be compatible with brands like TaoTao, Buyang, Coolsport, Kazuma, SUNL, Redcat, and similar manufacturers. The kit is marketed as a high-quality, easy-to-install option that delivers improved displacement and performance without requiring extensive modifications. It is not compatible with Apollo 110cc pit bikes, so riders should check their exact engine family before purchasing.
- 52.4mm bore for 110cc class engines
- Intended for TaoTao, Buyang, Coolsport, Kazuma, SUNL, Redcat and similar brands
- Not compatible with Apollo 110cc units
- Focus on ease of installation and performance gains
When planning an install, verify your engine’s bore and head clearance to ensure the piston ring kit and gasket set align with the cylinder head geometry. This kit suits riders seeking a straightforward upgrade with a clear emphasis on compatibility across a broad range of Chinese-brand engines.
TRKIMAL 52.4mm Big Bore Kit
TRKIMAL’s 52.4mm big bore kit is designed for a wide swath of 110cc four-stroke Chinese engines, including TaoTao, SSR, Kazuma, Panda, Lacoste, Coyote, Redcat, Roketa, Sunl, and Coolster. The kit provides a 52.4mm piston diameter, with specifications that include bolt hole spacing around 48mm x 50mm and a piston pin OD of 13mm. The package typically includes gaskets and necessary hardware, enabling a complete top-end refresh aimed at increasing displacement, power, and reliability for daily riders and hobbyists alike.
- 52.4mm bore for 110cc class engines
- Compatible with major Chinese brands
- Includes relevant gaskets and hardware for installation
Installation considerations include confirming bolt hole spacing compatibility with your cylinder head and ensuring the piston pin and ring sizes align with the kit’s components. This kit is well-suited for riders who want a robust 110cc upgrade with comprehensive packaging and clear compatibility across popular Chinese-engine platforms.
JooWing 250CC Big Bore Kit
The JooWing 250CC big bore kit targets 250cc air-cooled engines across ATVs, quad bikes, go-karts, dirt bikes, and pit bikes. With a 67mm bore, the kit significantly increases displacement for meaningful performance gains. The aluminum forging construction suggests durability and resistance to wear under higher loads, making it a compelling option for riders seeking a substantial upgrade on powered platforms that can accommodate a larger bore. Compatibility is focused on engines designed for 250cc displacement, so confirmation of your specific model is essential before purchase.
- 67mm bore for a substantial displacement increase
- Suitable for 250cc air-cooled engines
- Aluminum forged construction for durability
- Targeted at ATVs, dirt bikes, go-karts and pit bikes
Key considerations include ensuring the engine family and cooling system support a larger bore, checking piston ring and gasket compatibility, and planning for potential adjustments to exhaust height, carburation, and cooling airflow. This kit is best for riders who want a bold upgrade and have engines sized for 250cc-class performance while maintaining reliable operation across demanding riding conditions.
Buying Guide: How to Pick the Right Big Bore Kit
Key purchase considerations
When choosing a big bore kit for a pit bike, the bore size is the most obvious differentiator. A 56mm kit increases displacement more than a 52.4mm option, but fitment depends on your engine family and the head clearance. Always verify compatibility with your engine model (for example YinXiang 140cc or 1P56 variants) and check whether the kit includes a full top-end rebuild set (cylinder, piston, rings, gaskets, spark plug). Some kits also include cooling improvements or cooling-related design features to prevent overheating on extended high-rpm use.
Compatibility and fitment
Compatibility matters more than raw bore size. Even a large bore kit won’t deliver expected gains if it cannot seal properly against the head, or if the piston ring and head gasket sizes don’t align. Most 52.4mm kits target 110cc Chinese four-stroke engines, while 56mm options fit YinXiang/1P56-based platforms. For riders with non-standard engines, confirm bolt hole spacing, piston pin diameter, and overall cylinder height to avoid interference with the crankcase, head, or exhaust. If you ride in hot climates or do aggressive riding, consider kits that emphasize cooling performance or have robust gasket sets.
Installation effort and maintenance
Top-end upgrades can be straightforward for experienced hobbyists but challenging for newcomers. Kits that include gasket sets, rings, and spark plugs simplify the process, reducing the need for multiple trips to the parts store. Look for clear installation guidance and ensure you have the tools to compress rings, torque fasteners to spec, and correctly gap the piston rings. After installation, proper break-in procedures and regular maintenance—such as monitoring compression and oil quality—are crucial for long-term reliability.
Performance expectations and reliability
Big bore upgrades typically yield more torque and a higher peak power band, improving acceleration and hill-climbing ability. However, you may need to adjust the carburetion, exhaust, or cooling to maximize gains and maintain engine longevity. Durable materials, forged aluminum components, and complete gasket kits tend to offer better reliability under harsher riding conditions. Consider the intended use—recreational riding versus competitive racing—and choose a kit that aligns with your durability expectations and maintenance tolerance.
Value and after-sales support
Compare kit contents, warranty terms, and seller reputation when evaluating options. A kit that includes a full gasket set and spark plug reduces the number of separate purchases needed. Pay attention to customer reviews on fitment accuracy and any notes about required modifications. Good supplier support can help during installation and troubleshooting, which is especially valuable for first-time big bore upgrades.
In summary, the best big bore kit for your pit bike balances bore size with engine compatibility, includes essential components, and fits your maintenance plan. By examining bore options (52.4mm, 56mm, or larger), confirming compatibility with your engine family, and ensuring reliable installation, you can achieve meaningful performance gains while preserving engine life.