The Namura NA-40005-2K Top End Kit is designed for rebuilding the top end of select Yamaha 350 ATV engines. This 11:1 compression kit includes a piston, piston rings, wrist pin, retaining clips, top-end bearing, and gasket kit for a comprehensive installation. It is sized at 83.45 mm with a +0.50 mm oversize configuration and is intended for compatible applications using the original engine specifications and required cylinder preparation.
Designed for dependable performance and durability, the piston uses a hypereutectic casting process that increases silicon content to help control expansion, improve wear resistance, and withstand elevated cylinder temperatures. The MOS2, or Teflon/molybdenum, coated skirts use a rolled-on application process for a strong bond that helps reduce friction, improve heat transfer, and minimize the risk of cold seizures. Machined smooth heads help reflect combustion heat and reduce carbon buildup, while anodized domes improve heat resistance and piston durability.
Fitment includes 2006–2009 Yamaha YFM350X Wolverine 2WD [SRA] models and 2007–2012 Yamaha YFM350FG Grizzly 4WD [SRA] models. Confirm the model year, engine configuration, bore requirement, and cylinder condition before installation. Manufacturer part number: NA-40005-2K. Vendor part number: 186-40052.
Features:
- Complete Top End Kit: Includes piston, rings, wrist pin, retaining clips, top-end bearing, and gasket kit.
- 83.45 mm Bore Size: +0.50 mm oversize configuration for compatible Yamaha 350 engine rebuilds.
- 11:1 Compression Ratio: Supports the specified performance configuration for compatible applications.
- MOS2-Coated Skirts: 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 durability compared with non-anodized piston domes.
- Hypereutectic Casting: Higher silicon content helps reduce expansion, increase wear resistance, and tolerate higher cylinder temperatures.
- Fitment: Fits 2006–2009 Yamaha YFM350X Wolverine 2WD [SRA] and 2007–2012 Yamaha YFM350FG Grizzly 4WD [SRA] models.
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]