The Namura NA-40015 Standard Piston Kit is designed for select Yamaha 250cc ATV applications, including the Yamaha YFM250B Big Bear, YFM250B Bruin 2WD, and YFM250X Bear Tracker 2WD. This replacement piston kit features a standard 70.95 mm piston size and an 8.7:1 compression ratio, providing a reliable solution for engine rebuilding and maintenance.
Fitment includes the 2007–2009 Yamaha YFM250B Big Bear [SRA], 2005–2006 Yamaha YFM250B Bruin 2WD [SRA], and 1999–2003 Yamaha YFM250X Bear Tracker 2WD [SRA]. Verify the exact year, model, and original piston specifications before installation to ensure proper compatibility.
Manufacturer and vendor part number: Namura NA-40015. This kit is not compatible with OEM piston rings, and OEM rings will not work with the Namura piston. Use the correct replacement rings specified for this piston kit during assembly. Installation should be completed by a qualified technician using the manufacturer’s recommended procedures and clearances.
Features:
- Standard 70.95 mm piston size for select Yamaha 250cc ATV engines
- 8.7:1 compression ratio
- Fits 2007–2009 Yamaha YFM250B Big Bear [SRA]
- Fits 2005–2006 Yamaha YFM250B Bruin 2WD [SRA]
- Fits 1999–2003 Yamaha YFM250X Bear Tracker 2WD [SRA]
- Brand: Namura
- Manufacturer and vendor part number: NA-40015
- Will not accept OEM rings; OEM rings are not compatible with this piston
Fitment:
1992 Yamaha YFB250 Timberwolf 2WD [SRA]
1993 Yamaha YFB250 Timberwolf 2WD [SRA]
1994 Yamaha YFB250 Timberwolf 2WD [SRA]
1994 Yamaha YFB250FW Timberwolf 4WD [SRA]
1995 Yamaha YFB250 Timberwolf 2WD [SRA]
1995 Yamaha YFB250FW Timberwolf 4WD [SRA]
1996 Yamaha YFB250 Timberwolf 2WD [SRA]
1996 Yamaha YFB250FW Timberwolf 4WD [SRA]
1997 Yamaha YFB250 Timberwolf 2WD [SRA]
1997 Yamaha YFB250FW Timberwolf 4WD [SRA]
1998 Yamaha YFB250 Timberwolf 2WD [SRA]
1998 Yamaha YFB250FW Timberwolf 4WD [SRA]
1999 Yamaha YFB250FW Timberwolf 4WD [SRA]
1999 Yamaha YFM250X Bear Tracker 2WD [SRA]
2000 Yamaha YFB250FW Timberwolf 4WD [SRA]
2000 Yamaha YFM250X Bear Tracker 2WD [SRA]
2001 Yamaha YFM250X Bear Tracker 2WD [SRA]
2002 Yamaha YFM250X Bear Tracker 2WD [SRA]
2003 Yamaha YFM250X Bear Tracker 2WD [SRA]
2004 Yamaha YFM250X Bear Tracker 2WD [SRA]
2005 Yamaha YFM250B Bruin 2WD [SRA]
2006 Yamaha YFM250B Bruin 2WD [SRA]
2007 Yamaha YFM250B Big Bear [SRA]
2008 Yamaha YFM250B Big Bear [SRA]
2009 Yamaha YFM250B Big Bear [SRA]