The Namura NA-40004 Standard-Bore Piston Kit is designed for select Yamaha 660cc ATV and side-by-side applications. This replacement piston kit features a 99.97 mm standard-bore piston with a 9.2:1 compression ratio, providing a dependable fit for engine rebuilding and piston replacement service. The kit is intended for applications where the original piston and rings require replacement.
Fitment includes 2002–2008 Yamaha YFM660FG Grizzly 4WD with IRS and 2004–2006 Yamaha YXR660F Rhino 660. Verify the vehicle model, engine configuration, and existing piston specifications before ordering. The Namura NA-40004 piston kit uses its designated ring set and will not accept OEM rings; OEM rings are not compatible with this Namura piston. Proper installation should follow the vehicle manufacturer’s service procedures and applicable engine clearances.
Manufactured by Namura and supplied under vendor part number NA-40004, this piston kit is intended for professional engine repair, powersports maintenance, and replacement applications. Confirm standard-bore requirements and compatibility with the specific Yamaha model before installation.
Features:
- Standard Bore: 99.97 mm piston specification for compatible Yamaha 660cc engines
- Compression Ratio: 9.2:1 design for the specified application
- Application: Replacement piston kit for select Yamaha Grizzly 660 and Rhino 660 models
- Fitment: 2002–2008 Yamaha YFM660FG Grizzly 4WD with IRS
- Fitment: 2004–2006 Yamaha YXR660F Rhino 660
- Ring Compatibility: Will not accept OEM rings and OEM rings will not work with this piston
- Brand: Namura
- Manufacturer Part Number: NA-40004
- Vendor Part Number: NA-40004
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]