Restore reliable top-end performance with the Namura Top End Kit, part number NA-50000-4K. This 72.96 mm, 11:1 compression kit is designed for select Polaris 250 ATV applications and includes the essential components needed for a complete top-end rebuild: piston, piston rings, wrist pin, retaining clips, top-end bearing, and gasket kit. The kit is intended for direct fitment on specified Polaris Big Boss 250 4X6, Big Boss 250 6X6, and Trail Blazer 250 models.
The Namura piston uses a hypereutectic casting process with increased silicon content to help control expansion, improve wear resistance, and withstand elevated cylinder temperatures. Its MOS2, or Teflon/molybdenum, coated skirts are applied using a rolled-on process that creates a durable bond while helping reduce friction, improve heat transfer, and minimize the risk of cold seizure. A machined smooth head helps reflect combustion heat and reduce carbon buildup for added piston protection.
The anodized dome improves heat resistance and durability, making this piston suitable for demanding recreational and utility ATV use. The 11:1 compression design supports responsive engine operation when paired with the correct cylinder, fuel, and engine specifications. Verify the bore size, compression ratio, and model application before installation. This Namura kit fits 1991-1992 Polaris Big Boss 250 6X6 models; 1989-1992 Polaris Big Boss 250 4X6 models; and 1992-1993 and 2003-2004 Polaris Trail Blazer 250 models.
Features:
- Complete top-end kit: Includes piston, rings, wrist pin, retaining clips, top-end bearing, and gasket kit.
- Piston size: 72.96 mm bore size for compatible Polaris 250 ATV applications.
- Compression ratio: 11:1 design for specified engine configurations.
- MOS2-coated skirts: Rolled-on Teflon and molybdenum coating helps reduce friction, improve heat transfer, and minimize cold-seizure risk.
- Machined smooth head: Helps reflect combustion heat and reduce carbon buildup on the piston.
- Anodized dome: Improves heat resistance and piston durability.
- Hypereutectic construction: Increased silicon content helps reduce expansion and improve wear resistance at elevated cylinder temperatures.
- Fitment: Fits select 1989-1992 Polaris Big Boss 250 4X6, 1991-1992 Polaris Big Boss 250 6X6, and 1992-1993 and 2003-2004 Polaris Trail Blazer 250 models.
- Brand and manufacturer part number: Namura NA-50000-4K.
Fitment:
1989 Polaris Big Boss 250 4X6
1990 Polaris Big Boss 250 4X6
1990 Polaris Trail Blazer 250
1991 Polaris Big Boss 250 4X6
1991 Polaris Big Boss 250 6X6
1991 Polaris Trail Blazer 250
1991 Polaris Trail Boss 250 2X4
1992 Polaris Big Boss 250 4X6
1992 Polaris Big Boss 250 6X6
1992 Polaris Trail Blazer 250
1992 Polaris Trail Boss 250 2X4
1993 Polaris Trail Blazer 250
1993 Polaris Trail Boss 250 2X4
1994 Polaris Trail Blazer 250
1994 Polaris Trail Boss 250 2X4
1995 Polaris Trail Blazer 250
1995 Polaris Trail Boss 250 2X4
1996 Polaris Trail Blazer 250
1996 Polaris Trail Boss 250 2X4
1997 Polaris Trail Blazer 250
1997 Polaris Trail Boss 250 2X4
1998 Polaris Trail Blazer 250
1998 Polaris Trail Boss 250 2X4
1999 Polaris Trail Blazer 250
1999 Polaris Trail Boss 250 2X4
2000 Polaris Trail Blazer 250
2000 Polaris Xplorer 250 4X4
2001 Polaris Trail Blazer 250
2001 Polaris Xplorer 250 4X4
2002 Polaris Trail Blazer 250
2002 Polaris Xplorer 250 4X4
2003 Polaris Trail Blazer 250
2004 Polaris Trail Blazer 250
2005 Polaris Trail Blazer 250
2006 Polaris Trail Blazer 250