Cylinder Works Standard Bore Cylinder Kit with Head & Power Valve (422-20009K2 / 20009-K02) | Yamaha YZ250 (1999-2026)
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Complete high-performance standard bore cylinder and head kit engineered to deliver an ultimate, all-inclusive top-end refresh for legendary two-stroke motocross engines. Features a premium cast aluminum cylinder finished with a durable nickel silicon carbide (NSC) electroplate bore and diamond honed to exact specifications, bundled with a matching cylinder head, forged piston kit, complete top-end gaskets, wrist pin bearing, and a complete power valve kit to ensure optimal ring seal, reduced friction, and superior heat dissipation.
Specs & Details
- Manufacturer Part Number: 422-20009K2
- Alternative Part Number: Cylinder Works 20009-K02
- Kit Type: Complete Standard Bore Cylinder, Head, Piston, Gasket, and Power Valve Kit
- Bore Size: Standard (66.40 mm)
- Material & Construction: Cast aluminum cylinder with nickel silicon carbide plating, matched with high-strength forged piston components
Two-Stroke Vehicle Fitment
| Make | Model | Engine Type | Year Range |
| Yamaha | YZ 250 | Two-Stroke Motocross | 1999–2026 |
| Yamaha | YZ 250X | Two-Stroke Cross-Country | 2016–2026 |
TSO Garage Note
The ultimate master refresh package for a complete YZ250 top-end overhaul. When you are dealing with catastrophic wear, detonation damage, or just servicing a high-hour engine that needs everything from a fresh bore and piston to a new head casting and power valve components, this comprehensive kit saves you from hunting down individual part numbers. Dropping this in restores factory port timing, correct squish geometry, and crisp, reliable power delivery across the entire RPM range for the track or trail.
Compatibility
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