Wossner 8160DB Piston Kit - 2005-2022 Yamaha YZ125 YZ125X 2-Stroke Size B

Wossner 8160DB Premium Forged 2-Stroke Piston Kit - Size B

Keep your Yamaha 125 screaming at the front of the pack with the Wossner 8160DB Piston Kit. Specifically engineered for 2005-2021 YZ125 and 2020-2022 YZ125X cylinders that require a Size B fitment, this kit is designed to restore Factory Quality power and the crisp throttle response Yamaha is famous for. At Moto-House MX, we provide the precision-forged components required to maintain peak compression and high-RPM reliability in seasoned cylinders.

Forged from aerospace-grade aluminum alloy, this piston offers a superior strength-to-weight ratio compared to standard cast pistons. This is critical for 125cc engines that live at the top of the RPM range. The permanent skirt coating significantly reduces friction and piston rock, resulting in a quieter engine and improved mechanical longevity. This Size B piston (53.96mm) is designed for cylinders with a 54.01mm bore, providing the precise clearances needed for optimal performance in used cylinders.

Top Features: Wossner 8160DB Piston Kit

• Standard Size B (53.96mm): Precision-engineered for 54.01mm bores to maintain perfect tolerances in cylinders with standard wear.
• Aerospace Forged Alloy: Premium aluminum construction for maximum durability and thermal stability during intense motos.
• 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, maximizing the YZ125’s peak horsepower.
• Precision Lightweight Machining: Maintains structural strength while reducing reciprocating mass for faster acceleration.
• Complete Assembly: Kit includes the forged piston, high-performance ring, wrist pin, and clips.

Expert Pro-Tip: The Yamaha YZ125 engine is a masterpiece of small-bore engineering. Size B is the ideal choice for a cylinder that has been through several top-end refreshes, as it compensates for the natural microscopic wear of the Nikasil plating. Always use a new top-end gasket kit and inspect your power valve assembly to ensure the engine hits the pipe cleanly.

Fitment List

Year Range	Vehicle Brand	Vehicle Model & Size
2005-2021	Yamaha	YZ125
2020-2022	Yamaha	YZ125X (Off-Road)

Frequently Asked Questions

Q: What is the difference between Size A and Size B?
A: Size B (53.96mm) is exactly 0.01mm larger than Size A. This slight increase allows you to maintain the factory-specified piston-to-wall clearance as the cylinder wall experiences natural wear over time.

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

Q: Will this fit the redesigned 2022+ YZ125 motocross engine?
A: This kit fits the YZ125 motocross model up to 2021 and the YZ125X cross-country model through 2022. For the updated 2022+ YZ125 motocross engine, please check our other Wossner listings.

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.