Namura NA-10003-2 oversized piston kit (+0.50 mm) for the Honda 400cc engine, (11:1)

The Namura NA-10003-2 is an oversized piston kit (+0.50 mm) specifically engineered for the Honda 400cc engine family. It features a high-compression (11:1) design, which is an upgrade over the stock compression ratio (typically 9.1:1 on these models) for improved power and torque.

Vehicle Fitment

This kit is compatible with the following Honda ATV and Off-Road models:

• Honda TRX400EX Sportrax / FourTrax: 1999–2008

• Honda TRX400X: 2009, 2012–2014

• Honda XR400R: 1996–2004

Key Technical Specifications

The NAMURA Piston Kit NA-10003-2 is designed for cylinders that have been bored out to provide a fresh sealing surface:

• Bore Size: 85.47 mm (Standard is 84.97 mm)

• Oversize: +0.50 mm

• Compression Ratio: 11.0:1 High Compression (Requires higher octane fuel to prevent knocking)

• Piston Material: Hypereutectic aluminum alloy with anodized domes for 75% higher heat resistance.

• Skirt Coating: MOS2 (Molybdenum/Teflon) coated to reduce friction and eliminate "cold seizures."

• Kit Contents: Piston, OEM-quality rings, wrist pin, and circlips.

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