Namura .040 Over Bore Piston Kit for Yamaha Kodiak, Grizzly 400 2000-2008 85.5mm

Namura .040 Over Bore Piston Kit for Yamaha

This piston kit is a .040 overbore replacement component for Yamaha Kodiak and Grizzly 400 ATVs, featuring an 85.5mm diameter to restore engine compression and power.

Overview

This Namura .040 over bore piston kit for Yamaha Kodiak and Grizzly 400 models from 2000 to 2008 delivers a reliable top-end rebuild solution. It increases displacement slightly while maintaining OEM specifications for durability. The kit includes a piston, rings, wrist pin, and circlips for a complete installation.

Built For Performance

• High-strength cast aluminum alloy piston for long service life
• Moly-coated ring reduces friction and improves sealing
• Precision 85.5mm bore diameter matched to .040 overbore
• Includes wrist pin and retaining circlips for secure assembly
• Designed to meet or exceed OEM performance standards

Fits These Machines

• for Yamaha Kodiak 400 (2000-2008)
• for Yamaha Grizzly 400 (2000-2008)

On-The-Job Use

• Restoring top-end performance in worn engines
• Rebuilding ATVs after high-mileage operation
• Increasing compression for better throttle response
• Replacing damaged pistons due to overheating or wear

Specs At A Glance

Good To Know

Q: Do I need to re-plate or re-hone the cylinder when using this piston kit? A: Yes, an .040 overbore requires the cylinder to be bored and honed to the exact diameter to ensure proper clearance and ring seating.

Q: Is this kit compatible with the original head gasket? A: The kit uses standard gasket dimensions, but we recommend using a new head gasket and following torque specifications during assembly for a proper seal.

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