Namura NX-40098K Top End Kit for 2019-2021 Yamaha YZ85, 47.44 mm (+0.020 in) Ceramic Compression

The Namura NX-40098K Top End Kit is designed for select 2019, 2020, and 2021 Yamaha YZ85 models. This complete top-end solution includes a piston, piston rings, wrist pin, retaining clips, top-end bearing, and gasket kit for a convenient engine rebuild. With a 47.44 mm (+0.020 inch) piston size and an 11:1 compression ratio, the kit is engineered to support reliable performance and consistent operation in demanding motocross applications.

The piston features MOS2, a Teflon and molybdenum coating applied through a rolled-on process that creates a bond substantially stronger than many spray-on coatings. This coating helps improve heat transfer, reduce friction, and minimize the risk of cold seizures. The machined-smooth head helps reflect combustion heat, reduce carbon buildup, and protect the piston crown during operation.

An anodized dome improves heat resistance and durability, while the hypereutectic casting process increases silicon content for controlled expansion and enhanced wear resistance. These properties help the piston withstand elevated cylinder temperatures and maintain dependable fitment throughout the engine's operating range. The Namura NX-40098K kit is manufactured for direct fitment on 2019-2021 Yamaha YZ85 motorcycles and is intended for top-end service or replacement applications.

Features:

• Complete top-end kit includes piston, rings, wrist pin, clips, top-end bearing, and gasket kit
• 47.44 mm (+0.020 inch) piston size with an 11:1 compression ratio
• MOS2 Teflon and molybdenum-coated skirts help reduce friction, improve heat transfer, and minimize cold-seizure risk
• Machined-smooth piston head helps reflect combustion heat and reduce carbon buildup
• Anodized dome increases heat resistance and piston durability
• Hypereutectic casting process provides controlled expansion and improved wear resistance
• Direct fitment for 2019, 2020, and 2021 Yamaha YZ85 models
• Brand: Namura
• Manufacturer part number: NX-40098K
• Vendor part number: 185-4098