The NAMURA NA-10003K High-Compression Top End Kit is designed for select Honda TRX400X and TRX400EX Sportrax models. This complete top-end replacement kit includes a piston, piston rings, wrist pin, retaining clips, top-end bearing, and gasket kit for a convenient engine rebuild solution. The kit features an 11:1 compression ratio and a standard bore piston engineered for dependable performance and proper fitment on compatible Honda ATV applications.
NAMURA uses a hypereutectic casting process to provide increased silicon content, helping reduce thermal expansion while improving wear resistance and durability under elevated cylinder temperatures. The piston skirts feature a MOS2 coating made with Teflon and molybdenum. This rolled-on coating process creates a stronger bond than conventional spray-on coatings, helping reduce friction, improve heat transfer, and minimize the risk of cold seizures during operation.
The machined smooth piston head helps reflect combustion heat and limit carbon buildup, while the anodized dome improves heat resistance and overall piston durability. These design features support consistent engine operation and long-lasting service when installed with the correct components and manufacturer-recommended procedures. The NAMURA NA-10003K fits 2012–2014 Honda TRX400X models and 1999–2005 Honda TRX400EX Sportrax models. Verify the vehicle year, model, bore specification, and engine configuration before installation.
Features:
- Complete top-end kit includes piston, rings, wrist pin, retaining clips, top-end bearing, and gasket kit
- Standard bore piston with an 11:1 compression ratio for compatible Honda ATV engines
- MOS2 Teflon and molybdenum-coated skirts help reduce friction, improve heat transfer, and minimize cold-seizure risk
- Machined smooth piston head helps reflect combustion heat and reduce carbon buildup
- Anodized piston dome improves heat resistance and durability
- Hypereutectic casting process provides reduced expansion, increased wear resistance, and improved performance at higher cylinder temperatures
- Fits 2012–2014 Honda TRX400X and 1999–2005 Honda TRX400EX Sportrax models
- Brand: NAMURA
- Manufacturer part number: NA-10003K
- Vendor part number: 186-1003
Fitment:
1996 Honda XR400R
1997 Honda XR400R
1998 Honda XR400R
1999 Honda TRX400EX Sportrax
1999 Honda XR400R
2000 Honda TRX400EX Sportrax
2000 Honda XR400R
2001 Honda TRX400EX Sportrax
2001 Honda XR400R
2002 Honda TRX400EX Sportrax
2002 Honda XR400R
2003 Honda TRX400EX Sportrax
2003 Honda XR400R
2004 Honda TRX400EX Sportrax
2004 Honda XR400R
2005 Honda TRX400EX Sportrax
2006 Honda TRX400EX Sportrax
2007 Honda TRX400EX Sportrax
2008 Honda TRX400EX Sportrax
2009 Honda TRX400EX Sportrax
2012 Honda TRX400X
2013 Honda TRX400X
2014 Honda TRX400X