The NAMURA NA-40011K Top End Kit is a complete standard-bore replacement assembly designed for select Yamaha 450 ATV and UTV applications. This kit includes a piston, piston rings, wrist pin, wrist pin clips, top-end bearing, and gasket kit for a convenient upper-engine rebuild. It is engineered for reliable fitment and performance on compatible Yamaha Grizzly and Rhino models.
The piston uses a hypereutectic casting process with increased silicon content to help control expansion, improve wear resistance, and withstand elevated cylinder temperatures. The MOS2 Teflon/molybdenum-coated skirts use a rolled-on application process for a durable bond that helps reduce friction, improve heat transfer, and minimize the risk of cold seizures. The standard-bore design measures 84.45 mm and provides an 11:1 compression ratio for compatible applications.
Machined smooth heads help reflect combustion heat and reduce carbon buildup, while the anodized dome improves heat resistance and piston durability. These features support consistent operation and long-term service life when installed with the appropriate cylinder, crankshaft, and engine components. Always verify engine specifications and application details before installation.
Fitment: Fits 2006–2009 Yamaha YXR450F Rhino 450 models; 2007–2009 Yamaha YFM450FG Grizzly 4WD with IRS; and 2011–2014 Yamaha YFM450FGP Grizzly 4WD EPS with IRS. Manufacturer part number: NA-40011K. Vendor part number: 186-4011.
Features:
- Complete Top End Kit: Includes piston, piston rings, wrist pin, wrist pin clips, top-end bearing, and gasket kit.
- Standard Bore Design: 84.45 mm piston size with an 11:1 compression ratio for compatible Yamaha 450 engines.
- MOS2-Coated Skirts: Rolled-on Teflon/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 crown.
- Anodized Dome: Improves heat resistance and piston durability under demanding operating conditions.
- Hypereutectic Casting: Higher silicon content helps reduce expansion, increase wear resistance, and tolerate higher cylinder temperatures.
- Fitment: Designed for select Yamaha YFM450FGP Grizzly 4WD EPS with IRS, Yamaha YFM450FG Grizzly 4WD with IRS, and Yamaha YXR450F Rhino 450 models.
Fitment:
2003 Yamaha YFM450FA Kodiak 4WD [IRS]
2004 Yamaha YFM450FA Kodiak 4WD [IRS]
2005 Yamaha YFM450FA Kodiak 4WD [IRS]
2006 Yamaha YFM450FA Kodiak 4WD [IRS]
2006 Yamaha YFM450FX Wolverine 4WD [SRA]
2006 Yamaha YXR450F Rhino 450
2007 Yamaha YFM450FG Grizzly 4WD [IRS]
2007 Yamaha YFM450FX Wolverine 4WD [SRA]
2007 Yamaha YXR450F Rhino 450
2008 Yamaha YFM450FG Grizzly 4WD [IRS]
2008 Yamaha YFM450FX Wolverine 4WD [SRA]
2008 Yamaha YXR450F Rhino 450
2009 Yamaha YFM450FG Grizzly 4WD [IRS]
2009 Yamaha YFM450FX Wolverine 4WD [SRA]
2009 Yamaha YXR450F Rhino 450
2010 Yamaha YFM450FG Grizzly 4WD [IRS]
2010 Yamaha YFM450FX Wolverine 4WD [SRA]
2011 Yamaha YFM450FG Grizzly 4WD [IRS]
2011 Yamaha YFM450FGP Grizzly 4WD EPS [IRS]
2012 Yamaha YFM450FG Grizzly 4WD [IRS]
2012 Yamaha YFM450FGP Grizzly 4WD EPS [IRS]
2013 Yamaha YFM450FG Grizzly 4WD [IRS]
2013 Yamaha YFM450FGP Grizzly 4WD EPS [IRS]
2014 Yamaha YFM450FG Grizzly 4WD [IRS]
2014 Yamaha YFM450FGP Grizzly 4WD EPS [IRS]