Namura .040 Over Bore Top End Repair Kit for Yamaha YZ250 1999-2001 67.4mm

.040 Over Bore Top End Repair Kit for Yamaha YZ250

This top end repair kit for Yamaha YZ250 provides all necessary components for a .040 over bore rebuild, including piston, rings, wrist pin, and gasket set.

Overview

The Namura top end repair kit is designed for Yamaha YZ250 models from 1999 to 2001, delivering reliable performance for off-road racing and trail riding. With a 67.4mm bore size (.040 over standard), this kit restores compression and power. It is a cost-effective alternative to OEM components while meeting factory specifications.

Built For Performance

• Precision-cast piston matched to 67.4mm bore for optimal compression
• Chrome-plated steel rings provide long wear and consistent sealing
• Complete gasket set includes base gasket, head gasket, and exhaust gasket
• Heat-treated wrist pin with c-clips for secure connection
• Balanced piston weight reduces vibration and improves engine smoothness

Fits These Machines

• for Yamaha YZ250 (1999)
• for Yamaha YZ250 (2000)
• for Yamaha YZ250 (2001)

On-The-Job Use

• Motocross racing where top-end power and reliability are critical
• Trail riding and enduro competitions requiring consistent performance
• Two-stroke engine rebuilds for restoring worn top ends
• High-performance riding demanding precise piston-to-cylinder clearance

Specs At A Glance

Good To Know

Q: Can I use this kit on a 2002 Yamaha YZ250? A: No, this kit is specifically designed for 1999-2001 models; later years have different cylinder porting and bore dimensions.

Q: Do I need to replace the cylinder when using this overbore kit? A: If your cylinder is within service limits, it can be reused after honing to match the 67.4mm piston; always measure before installation.

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