Wossner 8559DA Piston Kit - 2001-2013 Yamaha WR250F / 2001-2004 YZ250F

Wossner 8559DA Premium Series Forged 4-Stroke Piston Kit - Standard Size A

Revitalize your Yamaha’s high-revving 250cc engine with the Wossner 8559DA Piston Kit. Specifically engineered for the 2001-2013 Yamaha WR250F and the early generation 2001-2004 YZ250F, this Premium Series forged kit is the professional choice for restoring Factory Quality performance. At Moto-House MX, we know these five-valve Yamaha engines are legendary for their durability; Wossner’s aerospace-grade forged components ensure your machine continues to deliver reliable power on the track or the trail.

Forged from aerospace-grade aluminum alloy, the 8559DA maintains a 12.5:1 compression ratio, providing a perfect balance of performance and long-term reliability. This piston features advanced radial boss machining and enhanced oiling slots for superior wrist pin lubrication—an essential upgrade for the high-RPM demands of a 250cc 4-stroke. The permanent skirt coating reduces internal friction and piston rock, resulting in a quieter engine and a safer break-in period.

Top Features: Wossner 8559DA Piston Kit

• Standard Size A (76.96mm Piston): Precision-engineered for the standard 77.00mm bore to restore original factory tolerances and compression.
• 12.5:1 Compression Ratio: Delivers consistent, tractable power that matches original equipment specifications for reliable performance.
• Premium Series Forging: High-strength aluminum construction offers superior thermal resistance and structural integrity over cast pistons.
• Enhanced Lubrication Design: Radial boss machining and annular grooves ensure the wrist pin stays lubricated during extended high-RPM use.
• Low-Friction Skirt Coating: Permanent coating minimizes mechanical noise and protects your cylinder walls from premature wear.
• Complete Assembly: Kit includes the forged piston, high-performance rings, wrist pin, and pin locks.

Expert Pro-Tip: The Yamaha WR250F and early YZ250F utilized a unique five-valve cylinder head design. When performing a top-end refresh with the 8559DA, always inspect your valve clearances and check the cam chain for stretch. Because these engines are often used for tight woods riding or high-revving motocross, using a fresh top-end gasket kit and premium synthetic oil is vital to ensuring your new forged piston performs at its peak for seasons to come.

Fitment List

Year Range	Vehicle Brand	Vehicle Model
2001-2013	Yamaha	WR250F
2001-2004	Yamaha	YZ250F

Frequently Asked Questions

Q: Is this a Standard Size piston?
A: Yes, this is the 76.96mm piston designed for the standard 77.00mm bore. It is the ideal choice for cylinders that are within factory service limits.

Q: Does this kit include the gaskets?
A: No, the kit includes the forged piston, rings, wrist pin, and locks. A top-end gasket kit is required for a professional, leak-free rebuild and is sold separately.

Q: Why choose Wossner for my Yamaha?
A: Wossner is a leader in forged piston technology. Their pistons are denser and stronger than OEM cast parts, allowing them to better handle the heat and mechanical stress of modern 4-stroke racing.

Recommended Pairings

• Complete Top End Gasket Set: Required for a professional seal and proper engine compression.
• Motorex Cross Power 4T Oil: Premium synthetic lubrication to protect your high-performance Yamaha engine.

Restore your machine’s power and precision today. Buy now at Moto-House MX!

Moto-House MX – Choice of Champions – is located in Clermont/Montverde, FL. The Best Motocross/UTV & ATV Shop in Central Florida. Stop by our local store in Montverde, FL or enjoy lightning-fast shipping across the USA.