CYLINDER WORKS Standard Bore Cylinder Kit 20009-K01
The CYLINDER WORKS 20009-K01 standard bore cylinder kit is a complete top-end solution for Yamaha YZ250 two-stroke combines an OEM-style cast aluminum cylinder with a precisely matched Vertex piston kit and top-end gaskets to restore factory performance, reliability and throttle response.
Key Product Highlights
- Ready-to-install, direct bolt-on replacement for the original YZ250 cylinder
- Standard 66.40 mm bore and 250 cc displacement for OEM-equivalent performance
- Nickel Silicon Carbide (Ni-SiC) plated cylinder bore for exceptional wear resistance
- Matched Vertex piston kit helps reduce engine noise and improve durability
- Supplied with all major components required for a complete top-end refresh
- Designed for Yamaha YZ250 2-stroke motocross models from 1999–2024, including the 2022 Monster Energy edition
- Made in the USA
Technical Specifications
| Product type | Standard bore cylinder kit (complete top-end kit) |
| Manufacturer | CYLINDER WORKS |
| Part number (SKU) | 20009-K01 |
| Engine type | 2-stroke (2-cycle) single-cylinder |
| Displacement | 250 cc (YZ250 standard displacement) |
| Cylinder bore | 66.40 mm (standard OEM bore) |
| Compression ratio | Approx. 10.6:1, stock-style compression |
| Cylinder material | Cast aluminum with Nickel Silicon Carbide (Ni-SiC) plated bore |
| Coating benefits | Improved hardness, reduced friction and long service life compared with uncoated bores |
| Piston brand | Vertex |
| Piston reference | Uses Vertex piston #22584 (matched to the supplied cylinder) |
| Application style | Direct bolt-on replacement, no replating or cylinder machining required |
| Country of manufacture | USA |
Kit Contents
The CYLINDER WORKS 20009-K01 kit is supplied as a comprehensive top-end package, simplifying engine service and reducing the need to source individual parts.
- Standard bore cylinder (cast aluminum, Ni-SiC plated)
- Vertex piston kit (piston, rings, pin, circlips)
- Top-end gasket kit (head and base gaskets, plus related seals as required)
- Wrist pin bearing for the piston pin
Design & Performance Benefits
- OEM-style fit and appearance: Cylinder exterior closely matches the original YZ250 casting, maintaining factory-like looks and compatibility with stock components.
- Matched piston and cylinder: Piston and bore are selected as a set to ensure correct clearances, reliable sealing and consistent compression.
- Ni-SiC plated bore: The Nickel Silicon Carbide surface offers high wear resistance, stable clearances and good heat transfer for demanding motocross and off-road use.
- Reduced engine noise: Properly matched piston-to-cylinder tolerances contribute to quieter mechanical operation compared with worn or mismatched components.
- Efficient service solution: Complete kit format streamlines a top-end rebuild, reducing workshop time compared with sending a worn cylinder out for replating.
Typical Use Cases
- Full top-end refresh on a Yamaha YZ250 2-stroke used for motocross, supercross or practice riding
- Restoration of older YZ250 models where the original cylinder is worn, damaged or previously replated
- Maintenance rebuilds on race or track bikes where consistent compression and power are important
- Replacement for a failed or scored cylinder following piston or ring failure
Vehicle Compatibility
This standard bore cylinder kit is engineered specifically for Yamaha YZ250 two-stroke covers a wide span of generations while retaining stock displacement and compression characteristics.
| Brand | Model | Year |
| Yamaha | YZ250 (2-stroke) | 1999–2024 |
| Yamaha | YZ250 Monster Energy Yamaha Racing Edition | 2022 |
Compatibility refers to standard configuration Yamaha YZ250 2-stroke motocross models within the listed years, using the original crankshaft stroke and connecting rod dimensions.
