The NAMURA NA-50002-4K Top End Kit is designed for select Polaris two-stroke ATV applications, including the 1994–1999 Polaris Sport 400L, 1994 Polaris 400L 2X4 and 4X4, and the 2003 Polaris Trail Blazer 400. This complete replacement kit supports dependable top-end service with a piston, piston rings, wrist pin, retaining clips, top-end bearing, and gasket kit included. Verify the model year and engine application before installation to ensure proper fitment.
Built using NAMURA performance-focused manufacturing processes, the piston features MOS2, or Teflon/Molybdenum, coated skirts. The rolled-on coating process creates a stronger bond than spray-applied alternatives while helping reduce friction, improve heat transfer, and minimize the risk of cold seizure. The hypereutectic casting process increases silicon content to help control expansion, improve wear resistance, and withstand elevated cylinder temperatures.
The piston also includes machined smooth heads to reflect combustion heat and help reduce carbon buildup, protecting the piston crown during operation. Anodized domes provide increased heat resistance and durability compared with non-anodized designs. Together, these features support consistent performance and long service life in demanding off-road use. This NAMURA top-end assembly is supplied as part number NA-50002-4K and is intended for compatible Polaris 400L and Trail Blazer 400 engines.
Features:
- Complete Top End Kit: Includes piston, 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 Heads: Helps reflect combustion heat and reduce carbon buildup on the piston crown.
- Anodized Domes: Improves heat resistance and durability for demanding engine operation.
- Hypereutectic Casting Process: Provides increased silicon content for controlled expansion, improved wear resistance, and greater resistance to high cylinder temperatures.
- Vehicle Fitment: Fits select 1994–1999 Polaris Sport 400L models, 1994 Polaris 400L 2X4 and 4X4 models, and the 2003 Polaris Trail Blazer 400.
- Manufacturer Part Number: NA-50002-4K.
- Vendor Part Number: 186-50024.
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