Namura Top End Kit for Yamaha YZ250, 67.96 mm Ceramic-Competition Piston, NX-40026-CK

The Namura NX-40026-CK Top End Kit is designed for select Yamaha YZ250 two-stroke applications and includes the essential components needed to refresh the top end. This ceramic-competition kit includes a piston, piston rings, wrist pin, circlips, top-end bearing, and gasket kit for a complete installation solution. The piston features a 67.96 mm bore size and an 11:1 compression ratio, providing a performance-focused replacement for compatible factory components.

Namura uses a hypereutectic casting process to increase silicon content, reduce expansion rates, and improve wear resistance under elevated cylinder temperatures. The piston skirts use a rolled-on MOS2 coating made from Teflon and molybdenum. This application method creates a durable bond while helping reduce friction, improve heat transfer, and minimize the risk of cold seizures during operation. The machined smooth head helps reflect combustion heat and reduce carbon buildup, supporting piston protection and consistent performance.

The anodized piston dome adds heat resistance and durability, with increased strength compared with non-anodized piston domes. This top-end kit fits 1992, 1993, and 1994 Yamaha YZ250 models. Verify the bore specification, compression ratio, and engine configuration before installation to ensure proper fitment. The manufacturer part number is NX-40026-CK, and the vendor part number is 185-4026C.

Features:

• Complete Top End Kit: Includes piston, rings, wrist pin, circlips, top-end bearing, and gasket kit.
• Application: Fits 1992, 1993, and 1994 Yamaha YZ250 models.
• Piston Size: 67.96 mm bore size with an 11:1 compression ratio.
• MOS2 Coated Skirts: Rolled-on Teflon and molybdenum coating helps reduce friction, improve heat transfer, and minimize cold-seizure risk.
• Machined Smooth Head: Helps reflect combustion heat and reduce carbon buildup on the piston crown.
• Anodized Dome: Improves heat resistance and durability compared with a non-anodized dome.
• Hypereutectic Casting: Higher silicon content supports reduced expansion, increased wear resistance, and durability at elevated cylinder temperatures.
• Manufacturer Part Number: NX-40026-CK.
• Vendor Part Number: 185-4026C.