Namura .040 Over Bore Piston Kit for Yamaha YZ250 & YZ250X fits 1999-2024 67.4mm

Namura .040 Over Bore Piston Kit for Yamaha

This .040 over bore piston kit is designed to restore compression in Yamaha YZ250 and YZ250X engines from 1999 to 2024 with a 67.4mm bore.

Overview

The Namura .040 over bore piston kit is a direct replacement for worn pistons in Yamaha two-stroke engines. This piston kit provides reliable power and durability for off-road and motocross riding. It is engineered for Yamaha YZ250 and YZ250X models requiring a 67.4mm bore.

Built For Performance

• Forged 4032 aluminum alloy for high strength and thermal stability
• Includes piston rings, wrist pin, and circlips for a complete replacement
• Precision machined to 67.4mm for .040 over bore applications
• Advanced skirt coating reduces friction and wear
• Designed for high-rpm performance in two-stroke engines
• Weight-matched for consistent engine balance

Fits These Machines

• for Yamaha YZ250 (1999-2024)
• for Yamaha YZ250X (1999-2024)

On-The-Job Use

• Restores lost compression in high-mileage YZ250 engines
• Ideal for motocross and off-road racing rebuilds
• Used in top-end rebuilds for improved throttle response
• Recommended for competition-level two-stroke maintenance

Specs At A Glance

Good To Know

Q: Is this piston kit a direct replacement for the OEM piston? A: This kit is a direct replacement when the cylinder is bored to .040 over size. Confirm your cylinder bore before ordering.

Q: What is the recommended break-in procedure? A: After installation, follow a standard two-stroke break-in with varying throttle loads for the first hour of operation.

Slight variation in finish or dimensions may occur between production runs, and fit can depend on serial number, so confirm compatibility before ordering.