The NAMURA NA-50002-6K Top End Kit is a complete replacement piston assembly designed for select Polaris 400 two-stroke ATV applications. This kit includes the piston, piston rings, wrist pin, wrist pin clips, top end bearing, and gasket kit needed for a thorough top-end rebuild. The 84.44 mm piston size provides a 1.50 mm oversize configuration for compatible cylinder applications.
Built using NAMURA’s hypereutectic casting process, the piston offers increased silicon content for controlled expansion, improved wear resistance, and reliable performance under elevated cylinder temperatures. The MOS2, or Teflon/molybdenum, coated skirts use a rolled-on application process that creates a durable bond while helping reduce friction, improve heat transfer, and minimize the risk of cold seizure during operation.
The machined smooth head helps reflect combustion heat and reduce carbon buildup on the piston crown. An anodized dome further improves heat resistance and durability, supporting dependable performance in demanding riding conditions. The included gasket kit, top end bearing, rings, wrist pin, and clips help simplify installation when servicing the upper engine assembly.
Fitment includes the 1994–1999 Polaris Sport 400L, 1994–1995 Polaris 400L 2X4, 1994 Polaris 400L 4X4, and 2003 Polaris Trail Blazer 400. Verify the model year, engine configuration, cylinder condition, and required piston oversize before installation. Manufacturer and vendor part number: NAMURA NA-50002-6K.
Features:
- Complete top end kit includes piston, rings, wrist pin, wrist pin clips, top end bearing, and gasket kit
- 84.44 mm piston size with a 1.50 mm oversize configuration for compatible applications
- MOS2 Teflon/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 controlled expansion, increased wear resistance, and improved high-temperature capability
- Fits select 1994–1999 Polaris Sport 400L, 1994–1995 Polaris 400L 2X4, 1994 Polaris 400L 4X4, and 2003 Polaris Trail Blazer 400 models
- Brand: NAMURA; Manufacturer and vendor part number: NA-50002-6K
Fitment:
1994 Polaris 400L 2X4
1994 Polaris 400L 4X4
1994 Polaris Sport 400L
1995 Polaris 400L 2X4
1995 Polaris Scrambler 400 4X4
1995 Polaris Sport 400L
1995 Polaris Xplorer 400 4X4
1996 Polaris Scrambler 400 4X4
1996 Polaris Sport 400L
1996 Polaris Xplorer 400 4X4
1997 Polaris Scrambler 400 4X4
1997 Polaris Sport 400L
1997 Polaris Xplorer 400 4X4
1998 Polaris Scrambler 400 4X4
1998 Polaris Sport 400L
1998 Polaris Xplorer 400 4X4
1999 Polaris Scrambler 400 4X4
1999 Polaris Sport 400L
1999 Polaris Xplorer 400 4X4
2000 Polaris Scrambler 400 2X4
2000 Polaris Scrambler 400 4X4
2000 Polaris Xplorer 400 4X4
2001 Polaris Scrambler 400 2X4
2001 Polaris Scrambler 400 4X4
2001 Polaris Xplorer 400 4X4
2002 Polaris Scrambler 400 2X4
2002 Polaris Scrambler 400 4X4
2002 Polaris Xplorer 400L
2003 Polaris Trail Blazer 400