The NAMURA NA-50026-2K Top End Kit is designed to restore dependable top-end performance for select Polaris ATV and UTV engines. This kit features an 88.39 mm piston with a 11:1 compression ratio and includes the piston, piston rings, wrist pin, retaining clips, top-end bearing, and gasket kit. It provides the core components needed for a thorough top-end rebuild while helping ensure proper fitment and reliable operation.
The piston uses a hypereutectic casting process to provide increased silicon content, reduced expansion, and improved wear resistance under elevated cylinder temperatures. Its MOS2, or Teflon and molybdenum, coated skirts are applied using a rolled-on process that creates a stronger bond than conventional spray-on coatings. This coating helps 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, while the anodized dome improves heat resistance and durability. Together, these features support consistent combustion performance and extended piston service life. The included gasket kit and top-end components make this NAMURA kit a practical choice for engine rebuilding and replacement applications.
Fitment: The NAMURA NA-50026-2K fits 2008–2012 Polaris Sportsman 400 HO 2x4 models, 2006–2007 Polaris Sportsman 450 models, and 2010–2012 Polaris Ranger 400 4x4 Midsize models. Verify the vehicle model, year, engine configuration, and required piston specifications before installation. Manufacturer part number: NA-50026-2K. Vendor part number: 186-50262.
Features:
- Complete top-end kit includes piston, rings, wrist pin, retaining clips, top-end bearing, and gasket kit
- 88.39 mm piston with 11:1 compression ratio for compatible Polaris applications
- MOS2 Teflon and molybdenum coated skirts help 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 reduced expansion and increased wear resistance
- Fits select 2006–2012 Polaris Sportsman 400 HO, Sportsman 450, and Ranger 400 4x4 Midsize models
Fitment:
2001 Polaris Sportsman 400 4X4
2002 Polaris Sportsman 400 4X4
2003 Polaris Sportsman 400 4X4
2004 Polaris Sportsman 400 4X4
2005 Polaris Sportsman 400 4X4
2006 Polaris Sportsman 450
2007 Polaris Sportsman 450
2008 Polaris Sportsman 400 HO 2x4
2009 Polaris Sportsman 400 HO 2x4
2010 Polaris Ranger 400 4X4 [Midsize]
2010 Polaris Sportsman 400 HO 2x4
2011 Polaris Ranger 400 4X4 [Midsize]
2011 Polaris Sportsman 400 HO 2x4
2012 Polaris Hawkeye 400 HO 2x4
2012 Polaris Ranger 400 4X4 [Midsize]
2012 Polaris Sportsman 400 HO 2x4
2013 Polaris Hawkeye 400 HO 2x4
2013 Polaris Ranger 400 4X4 [Midsize]
2014 Polaris Hawkeye 400 HO 2x4
2014 Polaris Ranger 400 4X4 [Midsize]