NAMURA Top End Kit 96.57 mm Standard Bore, 11:1 Compression for Polaris Sportsman 550 – NA-50011K

Restore top-end performance with the NAMURA Top End Kit, part number NA-50011K. Designed for the Polaris Sportsman 550, this standard-bore kit includes the primary components needed for a dependable piston replacement and top-end rebuild. The kit includes a piston, piston rings, wrist pin, retaining clips, top-end bearing, and gasket kit for convenient installation and proper engine service.

The piston features MOS2, or Teflon and molybdenum, coated skirts applied through a rolled-on process that creates a durable bond. This coating helps improve heat transfer, reduce friction, and minimize the risk of cold seizures. The machined smooth head reflects combustion heat and helps reduce carbon buildup, supporting piston protection and efficient engine operation. The 11:1 compression design is suited to applications requiring reliable replacement performance and consistent combustion.

An anodized dome improves heat resistance and durability, while the hypereutectic casting process increases silicon content for controlled expansion and improved wear resistance. These construction features help the piston withstand higher cylinder temperatures and demanding riding conditions. This NAMURA top-end kit is designed to fit 2010, 2011, 2012, and 2013 Polaris Sportsman 550 models. Verify the engine application and standard-bore requirement before installation.

Features:

• Complete top-end kit includes piston, rings, wrist pin, retaining clips, top-end bearing, and gasket kit
• 96.57 mm standard-bore piston with 11:1 compression ratio
• MOS2 Teflon and molybdenum coated skirt helps reduce friction, improve heat transfer, and minimize cold-seizure risk
• Machined smooth head helps reflect combustion heat and reduce carbon buildup
• Anodized dome improves heat resistance and piston durability
• Hypereutectic casting process provides controlled expansion, increased wear resistance, and improved high-temperature performance
• Fits 2010-2013 Polaris Sportsman 550 models
• Brand: NAMURA
• Manufacturer part number: NA-50011K
• Vendor part number: 186-5011