Restore reliable top-end performance with the Namura NX-40005K Standard Bore 11:1 Top End Kit. Designed for Yamaha PW50 models from 1990 through 1999, this complete kit includes the essential components needed for a thorough top-end rebuild, including a piston, piston rings, wrist pin, retaining clips, top-end bearing, and gasket kit. The standard-bore piston is engineered for direct fitment with the specified Yamaha PW50 applications.
The piston features Namura’s MOS2, or Teflon and molybdenum, coated skirts. This rolled-on coating process creates a strong bond designed to reduce friction, improve heat transfer, and help minimize the risk of cold seizures. The machined smooth head reflects combustion heat and helps reduce carbon buildup, supporting piston protection, consistent operation, and efficient engine performance.
An anodized dome improves heat resistance and durability, while the hypereutectic casting process adds silicon to help control expansion, increase wear resistance, and withstand elevated cylinder temperatures. With an 11:1 compression ratio, the kit is suited for riders and technicians seeking dependable replacement components for a Yamaha PW50 top-end service. Confirm the model year and engine specifications before installation to ensure proper fitment.
Namura manufacturer part number NX-40005K is supplied by the vendor under the catalog reference 185-4005. The kit is intended for Yamaha PW50 models manufactured from 1990 through 1999.
Features:
- Complete Top End Kit: Includes piston, rings, wrist pin, retaining clips, top-end bearing, and gasket kit.
- Application: Designed to fit Yamaha PW50 models from 1990 through 1999.
- Standard Bore: Provides a standard-bore replacement piston for compatible Yamaha PW50 engines.
- Compression Ratio: Features an 11:1 compression ratio for the specified application.
- MOS2-Coated Skirt: Teflon and molybdenum coating helps reduce friction, improve heat transfer, and minimize cold-seizure risk.
- Machined Smooth Head: Reflects combustion heat and helps reduce carbon buildup on the piston crown.
- Anodized Dome: Improves heat resistance and piston durability.
- Hypereutectic Casting: Increased silicon content helps reduce expansion, improve wear resistance, and withstand higher cylinder temperatures.
- Brand and Part Number: Namura NX-40005K manufacturer part number.
Fitment:
1990 Yamaha PW 50
1991 Yamaha PW 50
1992 Yamaha PW 50
1993 Yamaha PW 50
1994 Yamaha PW 50
1995 Yamaha PW 50
1996 Yamaha PW 50
1997 Yamaha PW 50
1998 Yamaha PW 50
1999 Yamaha PW 50
2000 Yamaha PW 50
2001 Yamaha PW 50
2002 Yamaha PW 50
2003 Yamaha PW 50
2004 Yamaha PW 50
2005 Yamaha PW 50
2006 Yamaha PW 50
2007 Yamaha PW 50
2008 Yamaha PW 50
2009 Yamaha PW 50
2012 Yamaha PW 50
2013 Yamaha PW 50
2014 Yamaha PW 50
2015 Yamaha PW 50
2016 Yamaha PW 50
2017 Yamaha PW 50
2018 Yamaha PW 50
2019 Yamaha PW 50
2020 Yamaha PW 50
2021 Yamaha PW 50