Restore top-end performance with the Namura NA-50012-4K Top End Kit, designed for select Polaris 850 engines. This kit includes a piston, piston rings, wrist pin, retaining clips, top-end bearing, and gasket kit for a comprehensive replacement solution. With an 11:1 compression ratio and an 87.93 mm piston size, the kit is suited for service, rebuild, and performance maintenance applications.
The Namura piston uses a hypereutectic casting process with increased silicon content to help control expansion, improve wear resistance, and withstand elevated cylinder temperatures. MOS2, or Teflon and molybdenum, coated skirts are applied using a rolled-on process that creates a strong bond while reducing friction, improving heat transfer, and helping minimize cold-seizure risk. Machined smooth heads help reflect combustion heat and reduce carbon buildup, while anodized domes provide added heat resistance and durability.
Manufacturer part number NA-50012-4K and vendor part number 186-50124 identify this Namura top-end assembly. Fitment includes the 2015–2017 Polaris Sportsman 850 SP, 2015–2017 Polaris Sportsman Touring 850 SP, 2014 Polaris Scrambler XP 850, 2014 Polaris Scrambler XP 850 EPS, 2012 Polaris Sportsman Touring 850 EPS, and 2013 Polaris Sportsman Touring 850 EPS. Verify engine configuration and application details before installation to ensure proper compatibility.
Features:
- Complete top-end kit includes piston, rings, wrist pin, retaining clips, top-end bearing, and gasket kit
- 87.93 mm 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 heads help reflect combustion heat and reduce carbon buildup
- Anodized piston domes provide increased heat resistance and durability
- Hypereutectic casting process delivers controlled expansion, improved wear resistance, and enhanced high-temperature performance
- Fits select Polaris Sportsman 850 SP, Sportsman Touring 850 SP, Sportsman Touring 850 EPS, and Scrambler XP 850 models
Fitment:
2012 Polaris Sportsman Touring 850 EPS
2013 Polaris Scrambler XP 850
2013 Polaris Scrambler XP 850 EPS
2013 Polaris Sportsman Touring 850 EPS
2013 Polaris Sportsman XP 850 EPS
2014 Polaris Scrambler XP 850
2014 Polaris Scrambler XP 850 EPS
2014 Polaris Sportsman Touring 850 EPS
2015 Polaris Sportsman 850 SP
2015 Polaris Sportsman Touring 850 SP
2016 Polaris Sportsman 850 SP
2016 Polaris Sportsman Touring 850 SP
2017 Polaris Sportsman 850 SP
2017 Polaris Sportsman Touring 850 SP
2018 Polaris Sportsman 850 SP
2018 Polaris Sportsman Touring 850 SP