Namura .040 Over Bore Piston Kit for Honda XR400R fits 1996-2004 Models 86mm

.040 Over Bore Piston Kit for Honda

This Namura .040 over bore piston kit is built for Honda XR400R models from 1996 to 2004, sized at 86mm. It restores compression and power when reboring the cylinder to the first oversize.

Overview

This Namura .040 over bore piston kit replaces the stock piston in Honda XR400R engines from 1996 through 2004, using an 86mm bore. It includes the piston, rings, wrist pin, and circlips for a complete top-end rebuild. Designed for trail and competition use, it maintains reliable compression and reduces blow-by.

Built For Performance

• High-silicon aluminum alloy casting for lightweight strength
• Precision-machined ring grooves for consistent sealing
• Molybdenum-coated wrist pin reduces friction
• Kit includes all necessary components for installation
• Oversized to clean up worn cylinder bores

Fits These Machines

• for Honda XR400R (1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004)

On-The-Job Use

• Rebuilding a high-mileage XR400R top end
• Restoring lost compression in enduro or dual-sport bikes
• Competition use where maximum reliability is required
• Trail riding and adventure riding maintenance cycles

Specs At A Glance

Good To Know

Q: Do I need to hone the cylinder before installing this piston? A: Yes, always hone the cylinder to the correct crosshatch pattern before installing any new piston to ensure proper ring seating and oil retention.

Q: Can this piston be used with a stock cylinder? A: Only if the cylinder has been bored to the corresponding .040 over size; it will not fit a standard 85mm bore without machining.

Slight variation in finish or dimensions may occur between production runs, and fit can depend on serial number, so confirm compatibility before ordering.