The Namura Top End Kit, manufacturer part number NA-40005-4K, is a complete replacement piston kit designed for select Yamaha 350 ATV applications. This 83.95 mm, 11:1 compression kit includes the piston, piston rings, wrist pin, retaining clips, top end bearing, and gasket kit needed for a top-end rebuild. It is engineered to support reliable performance, durability, and proper fitment during engine service.
The piston features MOS2, a Teflon and molybdenum coating applied through a rolled-on process for a stronger bond than conventional spray-on coatings. This coating helps improve heat transfer, reduce friction, and minimize the risk of cold seizures. The machined smooth head reflects combustion heat and helps reduce carbon buildup, while the anodized dome improves heat resistance and durability. Namura's hypereutectic casting process adds silicon to help control expansion, increase wear resistance, and withstand higher cylinder temperatures.
This Namura kit fits the 2006–2009 Yamaha YFM350X Wolverine 2WD with SRA and the 2007–2012 Yamaha YFM350FG Grizzly 4WD with SRA. Confirm the vehicle model, year, bore specification, and compression requirements before installation. The manufacturer part number is NA-40005-4K, and the vendor part number is 186-40054.
Features:
- Complete top-end kit includes piston, rings, wrist pin, retaining clips, top-end bearing, and gasket kit
- 83.95 mm piston size with 11:1 compression ratio
- MOS2 Teflon and molybdenum coated skirt helps reduce friction, improve heat transfer, and minimize cold-seizure risk
- Machined smooth piston head reflects combustion heat and helps reduce carbon buildup
- Anodized dome increases heat resistance and piston durability
- Hypereutectic casting process provides controlled expansion, wear resistance, and high-temperature performance
- Fits 2006–2009 Yamaha YFM350X Wolverine 2WD with SRA
- Fits 2007–2012 Yamaha YFM350FG Grizzly 4WD with SRA
- Brand: Namura
- Manufacturer part number: NA-40005-4K
- Vendor part number: 186-40054
Fitment:
1987 Yamaha YFM350ER Moto-4
1987 Yamaha YFM350FW Big Bear 4WD [SRA]
1987 Yamaha YFM350X Warrior
1988 Yamaha YFM350ER Moto-4
1988 Yamaha YFM350FW Big Bear 4WD [SRA]
1988 Yamaha YFM350X Warrior
1989 Yamaha YFM350ER Moto-4
1989 Yamaha YFM350FW Big Bear 4WD [SRA]
1989 Yamaha YFM350X Warrior
1990 Yamaha YFM350ER Moto-4
1990 Yamaha YFM350FW Big Bear 4WD [SRA]
1990 Yamaha YFM350X Warrior
1991 Yamaha YFM350ER Moto-4
1991 Yamaha YFM350FW Big Bear 4WD [SRA]
1991 Yamaha YFM350X Warrior
1992 Yamaha YFM350ER Moto-4
1992 Yamaha YFM350FW Big Bear 4WD [SRA]
1992 Yamaha YFM350X Warrior
1993 Yamaha YFM350ER Moto-4
1993 Yamaha YFM350FW Big Bear 4WD [SRA]
1993 Yamaha YFM350X Warrior
1994 Yamaha YFM350ER Moto-4
1994 Yamaha YFM350FW Big Bear 4WD [SRA]
1994 Yamaha YFM350X Warrior
1995 Yamaha YFM350ER Moto-4
1995 Yamaha YFM350FW Big Bear 4WD [SRA]
1995 Yamaha YFM350FX Wolverine 4WD [SRA]
1995 Yamaha YFM350X Warrior
1996 Yamaha YFM350FW Big Bear 4WD [SRA]
1996 Yamaha YFM350FX Wolverine 4WD [SRA]
1996 Yamaha YFM350U Big Bear 2WD [SRA]
1996 Yamaha YFM350X Warrior
1997 Yamaha YFM350FW Big Bear 4WD [SRA]
1997 Yamaha YFM350FX Wolverine 4WD [SRA]
1997 Yamaha YFM350U Big Bear 2WD [SRA]
1997 Yamaha YFM350X Warrior
1998 Yamaha YFM350FW Big Bear 4WD [SRA]
1998 Yamaha YFM350FX Wolverine 4WD [SRA]
1998 Yamaha YFM350U Big Bear 2WD [SRA]
1998 Yamaha YFM350X Warrior
1999 Yamaha YFM350FW Big Bear 4WD [SRA]
1999 Yamaha YFM350FX Wolverine 4WD [SRA]
1999 Yamaha YFM350U Big Bear 2WD [SRA]
1999 Yamaha YFM350X Warrior
2000 Yamaha YFM350FX Wolverine 4WD [SRA]
2000 Yamaha YFM350X Warrior
2001 Yamaha YFM350FX Wolverine 4WD [SRA]
2001 Yamaha YFM350X Warrior
2002 Yamaha YFM350FX Wolverine 4WD [SRA]
2002 Yamaha YFM350X Warrior
2003 Yamaha YFM350FX Wolverine 4WD [SRA]
2003 Yamaha YFM350X Warrior
2004 Yamaha YFM350BA Bruin 2WD [SRA]
2004 Yamaha YFM350FA Bruin 4WD [SRA]
2004 Yamaha YFM350FX Wolverine 4WD [SRA]
2004 Yamaha YFM350R Raptor
2004 Yamaha YFM350X Warrior
2005 Yamaha YFM350BA Bruin 2WD [SRA]
2005 Yamaha YFM350FA Bruin 4WD [SRA]
2005 Yamaha YFM350FX Wolverine 4WD [SRA]
2005 Yamaha YFM350R Raptor
2006 Yamaha YFM350BA Bruin 2WD [SRA]
2006 Yamaha YFM350FA Bruin 4WD [SRA]
2006 Yamaha YFM350R Raptor
2006 Yamaha YFM350X Wolverine 2WD [SRA]
2007 Yamaha YFM350FG Grizzly 4WD [SRA]
2007 Yamaha YFM350FGI Grizzly 4WD [IRS]
2007 Yamaha YFM350G Grizzly 2WD [SRA]
2007 Yamaha YFM350R Raptor
2007 Yamaha YFM350X Wolverine 2WD [SRA]
2008 Yamaha YFM350FG Grizzly 4WD [SRA]
2008 Yamaha YFM350FGI Grizzly 4WD [IRS]
2008 Yamaha YFM350G Grizzly 2WD [SRA]
2008 Yamaha YFM350R Raptor
2008 Yamaha YFM350X Wolverine 2WD [SRA]
2009 Yamaha YFM350FG Grizzly 4WD [SRA]
2009 Yamaha YFM350FGI Grizzly 4WD [IRS]
2009 Yamaha YFM350G Grizzly 2WD [SRA]
2009 Yamaha YFM350R Raptor
2009 Yamaha YFM350X Wolverine 2WD [SRA]
2010 Yamaha YFM350FG Grizzly 4WD [SRA]
2010 Yamaha YFM350FGI Grizzly 4WD [IRS]
2010 Yamaha YFM350G Grizzly 2WD [SRA]
2010 Yamaha YFM350R Raptor
2011 Yamaha YFM350FG Grizzly 4WD [SRA]
2011 Yamaha YFM350FGI Grizzly 4WD [IRS]
2011 Yamaha YFM350G Grizzly 2WD [SRA]
2011 Yamaha YFM350R Raptor
2012 Yamaha YFM350FG Grizzly 4WD [SRA]
2012 Yamaha YFM350FGI Grizzly 4WD [IRS]
2012 Yamaha YFM350G Grizzly 2WD [SRA]
2012 Yamaha YFM350R Raptor
2013 Yamaha YFM350FG Grizzly 4WD [SRA]
2013 Yamaha YFM350R Raptor
2014 Yamaha YFM350FG Grizzly 4WD [SRA]