Cylinder Works Big Bore Cylinder Kit is a complete top-end rebuild solution for Yamaha YZ 250 models, increasing displacement from 249cc to 295cc with a +5.6mm bore. This kit includes a high-quality nickel silicon carbide (NSC) electroplated cylinder for enhanced durability and reduced friction, along with a hand-matched Vertex big bore piston made from 2618 aluminum alloy for superior strength. Designed as a true bolt-on upgrade, this kit provides a noticeable power increase throughout the entire RPM range without requiring further engine modifications.

Features

• Complete top-end rebuild kit for big bore applications


• Includes cylinder, cylinder head, power valve kit, piston kit, top-end gasket kit, and wrist pin bearing


• Hand-matched Vertex big bore piston made from 2618 aluminum alloy for superior strength


• Nickel silicon carbide (NSC) electroplated bore for tighter tolerances and lower friction


• Provides increased power across the entire RPM range


• OEM appearance at a lower cost


• True bolt-on installation with no additional modifications required

Specifications

• Cylinder Diameter: 72 mm


• Cylinder Kit Type: Big Bore


• Displacement: 295 cc


• Engine Type: 2-Cycle


• Compression Ratio: Standard


• Size Over Standard: +5.60 mm


• Uses Vertex Piston #24079B

Vehicle Fitments

• Yamaha YZ 250 2T (1999-2024)