Cylinder Works Big Bore Cylinder Kit 21009-K01 — Yamaha YZ250 1999-2024

Product Description

Unlock more power and torque with the Cylinder Works Big Bore Cylinder Kit, designed specifically to take your Yamaha YZ250 to 295cc. This kit is the perfect solution for riders looking for a significant performance boost without the complexity of engine machine work. Engineered to look virtually identical to your OEM cylinder, it provides a clean, factory-style installation while delivering enhanced displacement for superior off-road performance.

Each kit comes complete with a precision-machined cylinder featuring a durable nickel silicon carbide sleeve for maximum heat dissipation and longevity. To ensure your engine runs quietly and efficiently, the kit includes a high-performance matching Vertex piston, along with all necessary rings, pins, clips, and gaskets for a total top-end rebuild. Proudly made in the USA, this kit is built to withstand the rigors of competitive riding.

Top Features: Cylinder Works Big Bore Kit

• Increases displacement to 295cc for improved low-to-mid range torque
• Includes matching Vertex piston for optimal performance and noise reduction
• Features nickel silicon carbide cylinder sleeve for extreme durability
• "Drop-in" design: No machine work required for installation
• Complete kit includes cylinder, piston, rings, pin, clips, and gasket set

Please review the detailed compatibility data below to ensure an exact fitment match for your motorcycle before finalizing your purchase.

Fitment List

Frequently Asked Questions

Q: Will this kit require any modifications to my engine cases?
A: No. This is a true drop-in kit. It is designed to fit your existing engine cases without the need for additional machining or boring.

Q: Does the increased displacement affect the reliability of my bike?
A: By using high-quality components like the included Vertex piston and the nickel silicon carbide-coated cylinder, this kit maintains excellent reliability while providing the added power of a 295cc build.

Expert Pro-Tip: Whenever you move to a Big Bore kit, you are increasing the volume of the combustion chamber, which significantly alters your fuel requirements. You MUST re-jet your carburetor to account for the additional displacement. Failing to adjust your jetting will result in a lean condition, which can cause detonation and catastrophic engine failure very quickly.

Recommended Pairings:
o Yamaha YZ250 Performance Parts & Upgrades
o Yamaha 2-Stroke Performance Parts
o High-Performance 2-Stroke Engine Oil

At Moto-House MX, we carry the best brands in motocross and off-road performance. Our team has over 40 years of experience helping riders get more out of their bikes. Every order ships fast from our Central Florida location.

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