This Wossner 57.25mm (+1.25 oversize) forged piston kit is engineered for Yamaha YZ125 models from 1986 to 1988. Manufactured in Germany, this piston is constructed using a forging process to ensure exceptional strength and durability. It incorporates an elliptical design to maintain a consistent bearing surface under heat expansion, reduce localised stress, and distribute thrust loads more evenly. This design supports efficient thermal management by optimising combustion chamber heat transfer to the cylinder walls, ensuring consistent performance in two-stroke engines.

Features

• Forged piston for increased strength and durability

• Elliptical design ensures uniform bearing surface during heat expansion

• Reduces localised pressure and distributes thrust loads to prevent piston collapse

• Engineered for optimal heat transfer from combustion chamber to cylinder walls

• Manufactured in Germany

Specifications

• Bore: 57.25mm

• Actual diameter: 57.19mm

• Displacement: 123 cm³

• Stroke: 50.00mm

• Clearance: 0.06mm

• Compression height: 30.00mm

• Compression ratio: 2-stroke

Cross-Reference OEM Part Numbers

• Piston Kit Part No.: 56-W559+125.WO

• Wossner Piston Kit No.: 8118D125

• Lock: CW16

• Pin: WP036

• Ring Set: RSB5725

Vehicle Fitments

• Yamaha YZ125 1986

• Yamaha YZ125 1987

• Yamaha YZ125 1988