The Namura NA-50080K Top End Kit is a complete standard-bore replacement package designed for select Polaris 800 engines. This 79.95 mm, 11:1 compression kit includes a piston, piston rings, wrist pin, retaining clips, top-end bearing, and gasket kit for a convenient rebuild solution. The kit is supplied under manufacturer part number NA-50080K and vendor part number 186-5080.
The piston features MOS2, or Teflon/molybdenum, coated skirts applied through a rolled-on process designed to provide a stronger bond than conventional spray-on coatings. This treatment helps reduce friction, improve heat transfer, and minimize the risk of cold seizures. Machined smooth heads reflect combustion heat and help reduce carbon buildup, supporting piston protection and consistent engine performance.
Anodized domes improve heat resistance and durability, while the hypereutectic casting process provides increased silicon content for reduced thermal expansion, added wear resistance, and improved ability to withstand elevated cylinder temperatures. These features make the Namura kit a practical choice for restoring top-end performance during engine service.
Fitment includes the 2010 Polaris Ranger Crew 800 4x4; 2008–2010 Polaris RZR 800; 2010 Polaris RZR 800 S; 2009–2010 Polaris Sportsman Big Boss 6X6 800; 2008 Polaris Sportsman Touring 800; and 2007 Polaris Sportsman X2 800 EFI. Verify the model, year, bore specification, and compression requirements before installation.
Features:
- Complete Top End Kit: Includes piston, rings, wrist pin, retaining clips, top-end bearing, and gasket kit.
- MOS2-Coated Skirts: Rolled-on Teflon/molybdenum coating helps reduce friction, improve heat transfer, and minimize cold-seizure risk.
- Machined Smooth Head: Helps reflect combustion heat and reduce carbon buildup for improved piston protection.
- Anodized Dome: Increases piston heat resistance and durability.
- Hypereutectic Construction: Provides reduced expansion, increased wear resistance, and improved high-temperature performance.
- Standard Bore Fitment: 79.95 mm standard-bore piston with an 11:1 compression ratio for select Polaris 800 applications.
- Vehicle Compatibility: Fits select Polaris Ranger, RZR, Sportsman Big Boss, Sportsman Touring, and Sportsman X2 800 models.
Fitment:
2005 Polaris Sportsman 800 EFI
2006 Polaris Sportsman 800 EFI
2007 Polaris Sportsman 800 EFI
2007 Polaris Sportsman X2 800 EFI
2008 Polaris RZR 800
2008 Polaris Sportsman Touring 800
2008 Polaris Sportsman X2 800 EFI
2009 Polaris RZR 800
2009 Polaris Sportsman Big Boss 6X6 800
2009 Polaris Sportsman Touring 800
2009 Polaris Sportsman X2 800 EFI
2010 Polaris Ranger 800 4x4
2010 Polaris Ranger 800 6X6
2010 Polaris Ranger Crew 800 4x4
2010 Polaris RZR 800
2010 Polaris RZR 800 S
2010 Polaris Sportsman 800 EFI
2010 Polaris Sportsman Big Boss 6X6 800