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The Athena Big Bore Race Cylinder Kit in Silver is designed for Yamaha YZ250 motorcycle owners (2003-2026) seeking enhanced performance. Its key benefit is a significant power increase through its larger bore design. A caveat is that it requires specialized, high-performance power valves, making OEM parts incompatible. This kit features an aluminum cylinder with a nickel carbide coating, an aluminum cylinder head with a removable bronze dome, and a forged race piston kit.
| Colour | Silver |
|---|---|
| Model Part Number | 09310440 |
| Brand | Athena |
This kit is designed for Yamaha YZ250 models manufactured between 2003 and 2026.
No, this kit requires the use of the specially designed, high-performance, hard anodized power valves included in the kit. OEM power valves are not compatible.
The kit includes an aluminum cylinder with nickel carbide coating, an aluminum cylinder head with a removable bronze dome, specialized power valves, an Athena top end gasket set with required seals and hardware, and a piston kit with forged race piston, rings, clips, and pin.
Yes, due to the specialized nature and performance focus of the kit, professional installation is highly recommended to ensure correct fitment and optimal performance.
Yes, the 'big bore' design significantly increases the engine's displacement, leading to substantial improvements in horsepower and torque.
While not strictly required for installation, pairing this kit with an upgraded exhaust system and appropriate carburetor tuning is recommended to fully capitalize on the performance gains.
The removable bronze dome allows for fine-tuning of the combustion chamber's shape and volume, enabling optimization of power delivery for specific riding conditions or preferences.
Verify proper installation of the power valves. Ensure the piston is installed in the correct orientation. Check for air leaks around the cylinder base and head. Confirm correct carburetor jetting for the increased displacement.
Check coolant level and flow (if liquid-cooled). Ensure the cooling system is free of obstructions. Verify proper air-fuel mixture; a lean condition can cause overheating. Consider a higher-performance radiator if operating in extreme conditions.
Confirm all fasteners are torqued to specification. Inspect the piston, rings, and cylinder walls for damage or excessive wear. Ensure the power valves are not binding or loose.
Check spark plug condition and gap. Verify fuel delivery and ensure the carburetor is clean and correctly jetted. Confirm compression is adequate.
Setup: Installation of the Athena Big Bore Race Cylinder Kit requires mechanical expertise. It involves replacing the stock cylinder and head components. Ensure all surfaces are clean before installation. Torque specifications for head and cylinder bolts must be followed precisely. Due to the specialized nature of the power valves, ensure they are correctly installed and aligned as per the kit's instructions. A professional installation is highly recommended to ensure proper fitment and performance.
Compatibility: This kit is specifically designed for Yamaha YZ250 models from 2003 to 2026. It is not compatible with OEM power valves; the kit includes specialized power valves that must be used. Ensure all other engine components are in good working order before installation.
Care: Regular maintenance is crucial for longevity. After riding, clean the exterior of the cylinder and head to prevent dirt and debris buildup. Monitor for any signs of leaks. Periodically inspect the piston and cylinder walls for wear, especially if used in demanding racing conditions. Proper engine oil and fuel mixture is essential for optimal lubrication and performance.
