Wossner 8217DB Piston Kit - 1999-2026 Yamaha YZ250 YZ250X 2-Stroke Size B

Wossner 8217DB Premium Forged 2-Stroke Piston Kit - Size B

Maintain the legendary performance of your Yamaha 2-stroke with the Wossner 8217DB Piston Kit. Specifically engineered for 1999-2026 Yamaha YZ250 and YZ250X cylinders that require a Size B fitment, this kit is the professional choice for restoring Factory Quality power and the broad, hard-hitting powerband Yamaha is famous for. At Moto-House MX, we provide the precision-forged components required for peak reliability and optimal piston-to-wall clearance.

Forged from aerospace-grade aluminum alloy, this piston provides a massive upgrade in strength and heat resistance over cast alternatives. The permanent skirt coating is a vital feature, reducing internal friction and piston rock for a quieter engine and smoother operation. This Size B piston (66.36mm) is designed for cylinders with a 66.41mm bore, making it the ideal selection for cylinders that have seen standard use and require a slightly larger diameter to maintain perfect compression.

Top Features: Wossner 8217DB Piston Kit

• Standard Size B (66.36mm): Precision-engineered for 66.41mm bores to maintain perfect tolerances in used cylinders.
• Aerospace Forged Alloy: Premium aluminum construction for maximum durability and thermal stability.
• Low-Friction Skirt Coating: Permanent coating reduces internal wear and mechanical noise for a more efficient engine.
• Single-Ring Racing Design: Optimized for reduced drag and high-RPM efficiency, ensuring maximum 250cc performance.
• Precision Lightweight Machining: Reduces reciprocating mass for faster revs and improved response.
• Complete Assembly: Kit includes the forged piston, high-performance ring, wrist pin, and clips.

Expert Pro-Tip: The Yamaha YZ250 engine is a masterpiece of longevity, but proper sizing is key. Size B is the standard "go-to" for the second or third top-end refresh on an original cylinder to compensate for natural microscopic wear of the Nikasil plating. Always ensure your power valve assembly is clean for maximum performance.

Fitment List

Year Range	Vehicle Brand	Vehicle Model & Size
1999-2026	Yamaha	YZ250
2016-2026	Yamaha	YZ250X (Off-Road)

Frequently Asked Questions

Q: What is the difference between Size A and Size B?
A: Size B (66.36mm) is exactly 0.01mm larger than Size A. This allows you to maintain the tight factory tolerances as your cylinder wall experiences very slight wear over time.

Q: Does this kit include the wrist pin bearing?
A: No, the kit includes the piston, ring, wrist pin, and clips. We highly recommend purchasing a new small-end bearing separately whenever you refresh your top end.

Q: Will this fit the YZ250X?
A: Yes, this piston is perfectly compatible with both the motocross-spec YZ250 and the cross-country YZ250X models from the years listed.

Recommended Pairings

• Top End Gasket Kit: Essential for a professional, leak-free engine rebuild.
• Motorex Cross Power 2T Oil: The ultimate synthetic lubrication choice for high-performance Yamaha 2-strokes.

Restore your Yamaha’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.