Wossner 8321DC Piston Kit - 2022-2026 Yamaha YZ125 YZ125X Size C

Wossner 8321DC Standard Series Forged 2-Stroke Piston Kit - Size C

Keep your Yamaha 125 at the front of the pack with the Wossner 8321DC Piston Kit. Specifically designed for the 2022-2026 Yamaha YZ125 and YZ125X models—including the 50th/70th Anniversary and Monster Energy editions—this Size C forged kit is the professional choice for seasoned cylinders. At Moto-House MX, we know that high-revving 125cc engines naturally wear their cylinder plating over time; Wossner’s Size C piston provides the precise fitment needed to restore compression and power to cylinders with moderate run time.

Forged from aerospace-grade aluminum alloy, the 8321DC features a performance-oriented single-ring design to minimize friction and allow for maximum RPM over-rev. Wossner utilizes optimized machining to ensure the piston remains incredibly lightweight, reducing reciprocating mass while maintaining superior strength in the crown and skirt walls. The permanent skirt coating is essential for 125cc racing, as it reduces piston rock and internal drag for a quieter engine and more efficient break-in. This Size C piston (53.97mm) is precision-matched for 54.02mm bores, making it the ideal solution for refreshing a used cylinder that has worn beyond the ideal limits for a Size A or B piston.

Top Features: Wossner 8321DC Piston Kit

• Size C (53.97mm): Precision-engineered for 54.02mm bores to restore factory-spec clearances in cylinders with moderate service wear.
• Single Ring Design: Minimizes internal drag and friction, allowing for the rapid revving and peak horsepower required for 125cc motocross.
• Aerospace-Grade Forging: Offers significantly higher durability and fatigue resistance than OEM cast pistons, critical for engines that live at high RPM.
• Low-Friction Skirt Coating: Permanent molybdenum disulphide coating protects the cylinder wall and reduces wear during high-heat operation.
• Optimized Reciprocating Mass: Engineered for lightness to improve throttle response without compromising structural integrity.
• Complete Assembly: Kit includes the forged piston, high-performance ring, wrist pin, and circlips.

Expert Pro-Tip: The modern YZ125 platform is a masterpiece of small-bore performance, but maintaining a tight piston-to-wall clearance is the only way to keep the "hit" in your powerband. Size C is the preferred choice for a top-end refresh when your cylinder is still in good condition but has worn slightly larger than factory-new specs. During installation, always clean your power valves and inspect your small-end bearing. Pairing this build with a fresh top-end gasket kit and premium premix oil will ensure your YZ125 continues to dominate the track.

Fitment List

Year Range	Vehicle Brand	Vehicle Model
2022-2026	Yamaha	YZ125 (Standard, Monster Energy, 50th/70th Anniversary)
2023-2026	Yamaha	YZ125X (Cross Country)

Frequently Asked Questions

Q: When should I choose a Size C piston?
A: Size C (53.97mm) is used for cylinders that have seen natural wear and have a bore size near 54.02mm. This restores the proper clearance to prevent piston slap and maintain maximum compression.

Q: Why choose Wossner for a 125cc race bike?
A: Wossner forged pistons are stronger and more reliable than cast OEM parts. In a 125, where the engine is often wide open, the added durability of a forged piston is essential for preventing catastrophic failure.

Q: Does this kit include the gasket set?
A: No, the kit includes the forged piston, ring, wrist pin, and clips. A complete top-end gasket set is sold separately and is required for a professional-grade rebuild.

Recommended Pairings

• Complete Top End Gasket Set: Ensure a professional, leak-free seal for your engine refresh.
• Yamalube 2-R Premix Oil: The gold standard for keeping high-performance Yamaha 2-strokes running clean and protected.

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.