The Namura NA-40004-4 piston kit is designed for select Yamaha 660 engines, including the YFM660FG Grizzly 4WD with independent rear suspension and the YXR660F Rhino 660. This oversized piston measures 100.97 mm, equivalent to a 1.00 mm oversize application, and uses a 9.2:1 compression ratio. It is intended for engine rebuilds requiring a replacement piston matched to a properly prepared cylinder.
Manufacturer and vendor part number: NA-40004-4. Brand: Namura. The kit is designed to fit 2002–2008 Yamaha YFM660FG Grizzly 4WD models and 2004–2006 Yamaha YXR660F Rhino 660 models, subject to cylinder condition and proper machining. Verify the existing bore, piston clearance, compression requirements, and model specifications before installation.
This Namura piston kit is not compatible with OEM piston rings, and its rings are not compatible with the OEM piston. Use the ring set supplied or specified for this Namura piston application. Professional installation is recommended, including cylinder inspection, boring or honing as required, ring-gap verification, and confirmation of piston-to-cylinder clearance. Following the applicable service procedures helps support reliable fitment and engine performance.
Features:
- Size: 100.97 mm piston diameter with a 1.00 mm oversize application
- Compression Ratio: 9.2:1
- Brand: Namura
- Manufacturer Part Number: NA-40004-4
- Vendor Part Number: NA-40004-4
- Fitment: 2002–2008 Yamaha YFM660FG Grizzly 4WD with independent rear suspension
- Fitment: 2004–2006 Yamaha YXR660F Rhino 660
- Compatibility: Will not accept OEM piston rings, and the supplied rings will not work with an OEM piston
Fitment:
2001 Yamaha YFM660R Raptor
2002 Yamaha YFM660FG Grizzly 4WD [IRS]
2002 Yamaha YFM660R Raptor
2003 Yamaha YFM660FG Grizzly 4WD [IRS]
2003 Yamaha YFM660R Raptor
2004 Yamaha YFM660FG Grizzly 4WD [IRS]
2004 Yamaha YFM660R Raptor
2004 Yamaha YXR660F Rhino 660
2005 Yamaha YFM660FG Grizzly 4WD [IRS]
2005 Yamaha YFM660R Raptor
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]