The NAMURA NX-40005-4K Top End Kit is designed for Yamaha PW 50 models from 1990 through 1999. This complete 40.96 mm, +1.00 mm oversize kit includes a piston, piston rings, wrist pin, retaining clips, top end bearing, and gasket kit for a convenient engine rebuild solution. The 11:1 compression design supports dependable performance and is intended for applications requiring a replacement top-end assembly.
The piston features a MOS2 Teflon and molybdenum-coated skirt applied through a rolled-on process for a durable bond. This coating helps improve heat transfer, reduce friction, and minimize the risk of cold seizures. The machined smooth head reflects combustion heat and helps limit carbon buildup, supporting piston protection and consistent engine operation.
An anodized dome increases heat resistance and durability, while the hypereutectic casting process provides increased silicon content for controlled expansion, added wear resistance, and improved tolerance of higher cylinder temperatures. The NAMURA NX-40005-4K is manufactured for direct fitment on 1990-1999 Yamaha PW 50 models. Verify the model year, bore requirement, and engine specifications before installation.
Features:
- Complete top end kit includes piston, rings, wrist pin, retaining clips, top end bearing, and gasket kit
- 40.96 mm bore with +1.00 mm oversize piston specification
- 11:1 compression ratio for the Yamaha PW 50 application
- MOS2 Teflon and molybdenum-coated skirt helps reduce friction, improve heat transfer, and minimize cold seizure risk
- Machined smooth piston head helps reflect combustion heat and reduce carbon buildup
- Anodized dome increases heat resistance and piston durability
- Hypereutectic casting process provides controlled expansion, improved wear resistance, and increased high-temperature capability
- Fits 1990-1999 Yamaha PW 50 models
- Brand: NAMURA
- Manufacturer part number: NX-40005-4K
- Vendor part number: 185-40054
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