Cylinder Works Big Bore Gasket Kit for Yamaha YZ250 1999-2020 21009-G01

When your YZ250's stock cylinder reaches its limits, a big bore kit is the direct path to increased displacement, improved throttle response, and measurable power gains. The Cylinder Works 21009-G01 delivers a complete, ready-to-install solution that eliminates guesswork and machine shop delays—giving you more time on the track and less time in the garage. This kit pairs precision-engineered components with U.S. manufacturing standards, ensuring reliability through season after season of aggressive riding.

What you're getting is a fully matched assembly designed to work as a system. The included Vertex pistons are optimized for the big bore cylinder's geometry, the gaskets seal critical surfaces without leaks, and the nickel silicon carbide plating resists wear from high combustion pressures. No machine work, no fitment surprises—just bolt it on and ride harder.

• Fits Yamaha YZ250 1999–2020
• MPN: 21009-G01
• Big bore cylinder kit
• Matched Vertex pistons included
• Gaskets, rings, pin, clips
• Nickel Silicon Carbide plating
• Bolt-on installation
• No machine work required
• Made in U.S.A.