Restore top-end performance with the NAMURA NA-40006K Top End Kit, designed for select Yamaha YFM400FA Kodiak 4WD and YFM400FB Big Bear 4WD models. This 83 mm standard-bore, 11:1 compression kit includes the essential components needed for a reliable top-end rebuild: piston, piston rings, wrist pin, wrist-pin clips, top-end bearing, and gasket kit. It is engineered for direct fitment on the applicable Yamaha ATV applications listed below.
The piston uses a hypereutectic casting process that increases silicon content to help control expansion, improve wear resistance, and withstand elevated cylinder temperatures. Its MOS2, or Teflon/molybdenum, coated skirts use a rolled-on application process for a strong coating bond. This finish helps reduce friction, improve heat transfer, and minimize the risk of cold seizures during operation. The machined-smooth piston head helps reflect combustion heat and reduce carbon buildup, while the anodized dome improves heat resistance and durability.
Fitment includes 1993–1995 Yamaha YFM400FA Kodiak 4WD with SRA and 2000–2006 Yamaha YFM400FB Big Bear 4WD with SRA. Verify the year, model, bore specification, and compression ratio before installation. Manufactured by NAMURA, this top-end kit is a practical replacement solution for rebuilding the upper engine assembly and supporting dependable ATV performance.
Features:
- Complete top-end kit includes piston, rings, wrist pin, clips, top-end bearing, and gasket kit
- 83 mm standard-bore piston with an 11:1 compression ratio for applicable Yamaha ATV engines
- 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 increases heat resistance and piston durability
- Hypereutectic casting process provides controlled expansion, wear resistance, and improved high-temperature capability
- Fits 1993–1995 Yamaha YFM400FA Kodiak 4WD with SRA
- Fits 2000–2006 Yamaha YFM400FB Big Bear 4WD with SRA
- Brand: NAMURA
- Manufacturer part number: NA-40006K
- Vendor part number: 186-4006
Fitment:
1993 Yamaha YFM400FA Kodiak 4WD [SRA]
1994 Yamaha YFM400FA Kodiak 4WD [SRA]
1995 Yamaha YFM400FA Kodiak 4WD [SRA]
1996 Yamaha YFM400FA Kodiak 4WD [SRA]
1997 Yamaha YFM400FA Kodiak 4WD [SRA]
1998 Yamaha YFM400FA Kodiak 4WD [SRA]
1999 Yamaha YFM400FA Kodiak 4WD [SRA]
2000 Yamaha YFM400 Big Bear 2WD [SRA]
2000 Yamaha YFM400FB Big Bear 4WD [SRA]
2001 Yamaha YFM400 Big Bear 2WD [SRA]
2001 Yamaha YFM400FB Big Bear 4WD [SRA]
2002 Yamaha YFM400 Big Bear 2WD [SRA]
2002 Yamaha YFM400FB Big Bear 4WD [SRA]
2003 Yamaha YFM400 Big Bear 2WD [SRA]
2003 Yamaha YFM400FB Big Bear 4WD [SRA]
2004 Yamaha YFM400 Big Bear 2WD [SRA]
2004 Yamaha YFM400FB Big Bear 4WD [SRA]
2005 Yamaha YFM400FB Big Bear 4WD [SRA]
2006 Yamaha YFM400FB Big Bear 4WD [SRA]
2007 Yamaha YFM400FBI Big Bear 4WD [IRS]
2008 Yamaha YFM400FBI Big Bear 4WD [IRS]
2009 Yamaha YFM400FBI Big Bear 4WD [IRS]
2010 Yamaha YFM400FBI Big Bear 4WD [IRS]