The Wossner 92mm Bore Piston Kit (Part No. 8603DA) is a high-performance forged piston designed for Yamaha YZ400F and WR400F models. Engineered for strength and durability, it optimizes heat transfer within the combustion chamber and features an elliptical design to ensure uniform load distribution, reducing localized pressure and preventing piston collapse. Manufactured in Germany, this piston maintains the OEM compression ratio for reliable engine performance.

Features

• High-strength forged piston construction


• Optimized heat transfer for improved combustion efficiency


• Elliptical design for even thrust load distribution


• Manufactured in Germany

Specifications

• Bore Size: 92mm


• Actual Bore Diameter: 91.95mm


• Compression Ratio: OEM


• OEM Compression Ratio: 11.0:1


• Displacement: 290cc


• Stroke: 61.20mm


• Clearance: 0.06mm


• Dome Volume: -4.80cm³


• Compression Height: 23.00mm

Cross-Reference OEM Part Numbers

• Lock P/N: CW18


• Pin P/N: WP053


• Ring Set P/N: 920XSY


• OEM Part Number: 5GR-11631-00-00

Vehicle Fitments

• Yamaha YZ400F (1998-1999)


• Yamaha WR400F (1998-1999)