Restore top-end performance with the Namura NX-40025-CKA Top End Kit, designed for select Yamaha YZ250 and YZ250X models. This complete kit includes a piston, piston rings, wrist pin, wrist-pin clips, top-end bearing, and gasket kit for a convenient engine rebuild solution. The 66.37 mm piston is engineered for dependable fitment and performance in compatible Yamaha two-stroke applications.
The piston features Namura’s MOS2, or Teflon and molybdenum, coated skirts. This rolled-on coating process creates a strong bond while helping reduce friction, improve heat transfer, and minimize the risk of cold seizures. The machined smooth head helps reflect combustion heat and reduce carbon buildup, supporting piston protection and consistent engine operation. An anodized dome adds heat resistance and durability, while the hypereutectic casting process provides increased silicon content for controlled expansion, added wear resistance, and improved performance at elevated cylinder temperatures.
Fitment includes 2002–2010 Yamaha YZ250 models and the 2016–2017 Yamaha YZ250X. Confirm the model year, bore size, compression specification, and cylinder condition before installation. This Namura kit is identified by manufacturer part number NX-40025-CKA and vendor part number 185-4025CA.
Features:
- Complete Top End Kit: Includes piston, rings, wrist pin, clips, top-end bearing, and gasket kit.
- MOS2-Coated Skirts: Helps reduce friction, improve heat transfer, and reduce the possibility of cold seizures.
- Machined Smooth Head: Reflects combustion heat and helps limit carbon buildup for improved piston protection.
- Anodized Dome: Increases heat resistance and durability compared with non-anodized piston domes.
- Hypereutectic Casting: Provides controlled expansion, increased wear resistance, and improved durability at higher cylinder temperatures.
- Piston Size: 66.37 mm bore specification for compatible Yamaha applications.
- Fitment: Fits 2002–2010 Yamaha YZ250 and 2016–2017 Yamaha YZ250X models.
- Part Numbers: Manufacturer part number NX-40025-CKA and vendor part number 185-4025CA.
Fitment:
2002 Yamaha YZ250
2003 Yamaha YZ250
2004 Yamaha YZ250
2005 Yamaha YZ250
2006 Yamaha YZ250
2007 Yamaha YZ250
2008 Yamaha YZ250
2009 Yamaha YZ250
2010 Yamaha YZ250
2011 Yamaha YZ250
2012 Yamaha YZ250
2013 Yamaha YZ250
2014 Yamaha YZ250
2015 Yamaha YZ250
2016 Yamaha YZ250
2016 Yamaha YZ250X
2017 Yamaha YZ250
2017 Yamaha YZ250X
2018 Yamaha YZ250
2018 Yamaha YZ250X
2019 Yamaha YZ250
2019 Yamaha YZ250X
2020 Yamaha YZ250
2020 Yamaha YZ250X
2021 Yamaha YZ250
2021 Yamaha YZ250X
2022 Yamaha YZ250
2022 Yamaha YZ250X