WOSSNER 77mm PISTON KIT A, YAMAHA YZ250F 14-15, WR250F 15-17, YZ250FX 15-16

This Wossner forged piston kit, part number 8893DA, features a standard 77mm bore with an actual piston size of 76.96mm. It is engineered for TM MX-F450 (2009–2010), MX-Fi450 (2011), and EN-Fi450 (2011) models. Manufactured in Germany, the piston is designed for high-performance four-stroke applications, offering superior heat transfer, strength, and pressure distribution due to its elliptical profile.

Features

• Forged construction for strength and long-lasting durability
• Elliptical design for uniform expansion and thrust load balance
• Optimized for heat transfer in high-performance engines
• Made in Germany
• Direct OEM replacement
• Easy to install; professional installation recommended if unsure

Specifications

• Bore Size: 77.00mm
• Actual Piston Size: 76.96mm
• Displacement: 249cm³
• Stroke: 53.60mm
• Clearance: 0.05mm
• Dome Volume: -3.00cm³
• Wossner Compression Ratio: 13.70:1
• OEM Compression Ratio: 13.50:1
• Compression Height: 20.20mm

Cross-Reference OEM Part Numbers

• 40116M07700
• 1SM-11631-01-00
• CW16 (Lock)
• WP087 (Pin)
• 770XAS-2 (Ring Set)

Vehicle Fitments

• TM MX-F450 (2009–2010)
• TM MX-Fi450 (2011)
• TM EN-Fi450 (2011)