Wossner forged piston kit designed for high compression and performance. Engineered for optimal heat transfer to cylinder walls, ensuring efficient combustion. The elliptical design provides a uniform bearing surface under heat expansion, reducing localized pressure and evenly distributing thrust loads to prevent piston collapse. Manufactured in Germany to high-quality standards.

Features

• High-compression forged piston for enhanced performance


• Optimized heat transfer for efficient combustion


• Elliptical design to prevent piston collapse


• Manufactured in Germany

Specifications

• Bore Size: 92.02mm


• Actual Bore Diameter: 91.97mm


• Displacement: 399 cm³


• Stroke: 60.10mm


• Clearance: 0.05mm


• Wossner Compression Ratio: 13.50:1


• OEM Compression Ratio: 12.50:1


• Dome Volume: -4.60 cm³


• Compression Height: 24.10mm


• Theoretical Weight: Not specified

Included Components

• Lock Part Number: CW18


• Pin Part Number: WP053


• Ring Set Part Number: 920XSY

Vehicle Fitments

• Yamaha WR400F (1998-1999)


• Yamaha YZ400F (1998-1999)