The Wossner 72.50mm Bore Piston Kit (Part No. 8659D150) is a high-performance forged piston designed for Yamaha YFM250 Timberwolf, YFB250 Bear Tracker, Bruin, and Big Bear models. Engineered for strength and durability, it optimizes heat transfer within the combustion chamber and features an elliptical design to ensure even 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: 72.50mm


• Actual Bore Diameter: 72.44mm


• Compression Ratio: OEM


• OEM Compression Ratio: 9.50:1


• Displacement: 229cc


• Stroke: 58.00mm


• Clearance: 0.06mm


• Dome Volume: -4.70cm³


• Compression Height: 23.80mm

Cross-Reference OEM Part Numbers

• Lock P/N: CW16


• Pin P/N: WP041


• Ring Set P/N: 725XDS

Vehicle Fitments

• Yamaha YFM250 Timberwolf (1990-2000)


• Yamaha YFB250 Bear Tracker (2000-2004)


• Yamaha Bruin (2005-2006)


• Yamaha Big Bear (2007-2009)