Restore top-end performance with the Namura NX-40025KA Top End Kit, designed for select Yamaha YZ250 and YZ250X models. This kit includes a piston, piston rings, wrist pin, retaining clips, top-end bearing, and gasket kit for a comprehensive engine rebuild solution. The 66.35 mm standard-bore piston and 11:1 compression ratio are engineered for compatible Yamaha two-stroke applications.
Namura uses a hypereutectic casting process to provide increased silicon content, reduced expansion, and improved wear resistance under elevated cylinder temperatures. The piston skirt features a rolled-on MOS2 coating containing Teflon and molybdenum, 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, while the anodized dome improves heat resistance and piston durability.
This Namura top-end kit fits the 2016 and 2017 Yamaha YZ250X, as well as Yamaha YZ250 models from 2002 through 2009. Confirm the motorcycle year, model, bore specification, and engine configuration before installation. Manufacturer part number: NX-40025KA. Vendor part number: 185-4025A.
Features:
- Complete top-end kit includes piston, rings, wrist pin, retaining clips, top-end bearing, and gasket kit
- MOS2-coated piston skirts help reduce friction, improve heat transfer, and reduce the risk of cold seizures
- Machined smooth piston head helps reflect combustion heat and limit carbon buildup
- Anodized piston dome increases heat resistance and durability
- Hypereutectic casting process provides reduced expansion and improved wear resistance
- 66.35 mm standard-bore piston with an 11:1 compression ratio
- Fits 2016-2017 Yamaha YZ250X and 2002-2009 Yamaha YZ250 models
- Brand: Namura; Manufacturer part number: NX-40025KA; Vendor part number: 185-4025A
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