Wossner 8302DC Piston Kit - 2005-2021 Yamaha YZ125 YZ125X Standard Size C

Wossner 8302DC Standard Series Forged 2-Stroke Piston Kit - Standard Size C

Bring the snap and reliability back to your Yamaha small-bore with the Wossner 8302DC Piston Kit. Precision-engineered for the 2005-2021 Yamaha YZ125 and the 2020-2022 YZ125X, the "Size C" forged kit is the expert choice for cylinders that have seen high hours of use. At Moto-House MX, we know that after many seasons of wide-open throttle, 125cc cylinder bores naturally expand; this +0.02mm Size C kit provides the precise fitment needed to restore a tight seal and eliminate power loss in worn bores.

Forged from high-performance aerospace aluminum alloy, the 8302DC is significantly more durable and heat-resilient than stock cast pistons. It features a dual-ring configuration, offering superior secondary compression and enhanced heat transfer from the piston to the cylinder wall—a vital feature for small-bore engines that operate at the edge of their RPM range. To ensure long-term performance, Wossner applies a permanent molybdenum disulphide skirt coating that reduces friction and prevents piston rock. Precision-machined for 54.02mm bores, this 53.97mm piston kit allows you to extend the life of your Yamaha cylinder before needing a replate.

Top Features: Wossner 8302DC Piston Kit

• Standard Size C (53.97mm): Specifically designed for 54.02mm bores to compensate for moderate cylinder wear and restore factory-level compression.
• Dual Ring Design: Enhances cylinder sealing and cooling efficiency, maintaining a reliable powerband during long motos or technical off-road loops.
• Aerospace-Grade Forging: Built to withstand high-RPM stress and mechanical fatigue far better than original cast alternatives.
• Low-Friction Skirt Coating: Permanent skirt treatment minimizes internal drag, protects the cylinder wall, and ensures a quieter engine.
• Optimized Lightness: Expertly machined to reduce reciprocating mass, ensuring the YZ125 retains its lightning-fast throttle response.
• Complete Assembly: Includes the forged Size C piston, performance rings, wrist pin, and circlips.

Expert Pro-Tip: The Yamaha YZ125 is a high-performance machine that requires perfect tolerances for peak horsepower. If your cylinder has seen significant use and measures slightly beyond factory Size A or B specs, moving to a Wossner Size C (53.97mm) is the professional way to bring your piston-to-wall clearance back to perfection. Always use a precision bore gauge to confirm your cylinder measures 54.02mm before installation. For a professional-grade rebuild, always install with a fresh top-end gasket kit and utilize premium 2-stroke oil to protect your investment.

Fitment List

Year Range	Vehicle Brand	Vehicle Model
2005-2021	Yamaha	YZ125
2020-2022	Yamaha	YZ125X

Frequently Asked Questions

Q: When should I choose Size C instead of Size A or B?
A: Size C (53.97mm) is used when the cylinder bore has worn larger (to 54.02mm) due to high hours. This slightly larger piston restores the tight seal necessary for peak power and prevents "piston slap."

Q: Is this kit compatible with the YZ125X off-road model?
A: Yes, this kit is fully compatible with both the YZ125 motocross bike and the YZ125X cross-country model within the specified year ranges.

Q: Do forged pistons last longer than cast ones?
A: Generally, yes. The forging process makes the metal denser and much more resistant to the structural fatigue and cracking that can occur with cast pistons in high-performance 2-stroke engines.

Recommended Pairings

• Complete Top End Gasket Set: Ensure a leak-free rebuild and maintain correct squish heights with fresh gaskets.
• Motul 800 2T Factory Line: The ultimate high-performance lubricant to keep your new forged piston protected in racing conditions.

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.