The Namura NA-40010-2K Top End Kit is designed for rebuilding the upper end of select Yamaha 660cc engines. This 100.47 mm +0.020 in oversize kit features an 11:1 compression ratio and includes the piston, piston rings, wrist pin, retaining clips, top-end bearing, and gasket kit needed for a comprehensive installation. It is engineered for dependable fitment and performance in compatible Yamaha ATV and side-by-side applications.
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 are applied using a rolled-on process that creates a durable bond while helping transfer heat, reduce friction, and minimize the risk of cold seizures. Machined smooth heads help reflect combustion heat and reduce carbon buildup, while the anodized dome improves heat resistance and durability.
This Namura top-end rebuild kit fits 2002–2008 Yamaha YFM660FG Grizzly 4WD IRS models and 2004–2006 Yamaha YXR660F Rhino 660 models, provided the engine has been prepared for the specified oversize piston. Confirm cylinder condition, bore requirements, compression specifications, and year-specific application details before installation. The manufacturer part number and vendor part number are both NA-40010-2K.
Features:
- Complete Top End Kit: Includes piston, rings, wrist pin, retaining clips, top-end bearing, and gasket kit.
- Oversize Piston: 100.47 mm, or +0.020 inch, piston size with an 11:1 compression ratio for compatible rebuilt engines.
- MOS2-Coated Skirts: Rolled-on Teflon/Molybdenum coating helps create a strong bond while reducing friction, improving heat transfer, and helping prevent cold seizures.
- Machined Smooth Head: Helps reflect combustion heat and reduce carbon buildup on the piston crown.
- Anodized Dome: Improves heat resistance and piston durability in demanding operating conditions.
- Hypereutectic Construction: Higher silicon content helps reduce expansion, improve wear resistance, and tolerate increased cylinder temperatures.
- Fitment: Fits 2002–2008 Yamaha YFM660FG Grizzly 4WD IRS models and 2004–2006 Yamaha YXR660F Rhino 660 models.
- Brand and Part Number: Namura NA-40010-2K; manufacturer and vendor part number NA-40010-2K.
Fitment:
2002 Yamaha YFM660FG Grizzly 4WD [IRS]
2003 Yamaha YFM660FG Grizzly 4WD [IRS]
2004 Yamaha YFM660FG Grizzly 4WD [IRS]
2004 Yamaha YXR660F Rhino 660
2005 Yamaha YFM660FG Grizzly 4WD [IRS]
2005 Yamaha YXR660F Rhino 660
2006 Yamaha YFM660FG Grizzly 4WD [IRS]
2006 Yamaha YXR660F Rhino 660
2007 Yamaha YFM660FG Grizzly 4WD [IRS]
2007 Yamaha YXR660F Rhino 660
2008 Yamaha YFM660FG Grizzly 4WD [IRS]