The NAMURA NA-50012-BK Top End Kit is designed for select Polaris 850 ATV applications and provides the essential components needed to service the upper end of the engine. This kit includes a piston, piston rings, wrist pin, retaining clips, top-end bearing, and gasket kit for a comprehensive replacement solution. The 86.94 mm piston is engineered for a 11:1 compression ratio and is suitable for the listed Polaris Sportsman, Sportsman Touring, and Scrambler XP 850 models.
NAMURA uses a hypereutectic casting process to increase silicon content, helping reduce expansion rates while improving wear resistance and the ability to withstand elevated cylinder temperatures. The piston skirts feature a rolled-on MOS2 coating made with Teflon and molybdenum. This bonded coating is designed to reduce friction, improve heat transfer, and help minimize the risk of cold seizures during operation.
The piston also features machined smooth heads to reflect combustion heat and help reduce carbon buildup, supporting piston protection and consistent engine performance. Anodized domes improve heat resistance and durability, providing added protection in demanding riding conditions. The kit is intended for direct service of compatible original-equipment engine configurations; verify the engine model and existing bore specifications before installation.
Fitment includes 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. The manufacturer part number is NA-50012-BK, and the vendor part number is 186-5012B.
Features:
- Complete top-end service kit includes piston, rings, wrist pin, retaining clips, top-end bearing, and gasket kit
- 86.94 mm piston with an 11:1 compression ratio for compatible Polaris 850 engine applications
- 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 improves heat resistance and piston durability
- Hypereutectic casting process provides reduced expansion, increased wear resistance, and improved high-temperature performance
- Fits select Polaris Sportsman, Sportsman Touring, and Scrambler XP 850 models
- Brand: NAMURA
- Manufacturer part number: NA-50012-BK
- Vendor part number: 186-5012B
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