790M08400 .120 Piston 84mm +3mm for Yamaha Wave Runner III GP 700 1994-97

Oversize Piston for Yamaha Wave Runner III GP 700

This Wiseco oversize piston with part numbers 790M08400 and a 84 mm bore, +3 mm over standard, replaces worn pistons in 1994-1997 Yamaha Wave Runner III GP 700 watercraft engines after cylinder boring.

Overview

This .120 oversize piston for Yamaha Wave Runner III GP 700 restores compression and power on engines that have been bored to 84 mm. The +3 mm piston for Yamaha Wave Runner III GP 700 is intended for rebuilds where cylinder wear requires an oversize bore to clean up the walls. Riders and mechanics use this piston to bring tired 700cc watercraft engines back to life.

Built For Performance

• 84 mm bore, +3 mm over standard, .120 oversize
• Manufactured by Wiseco with part numbers 790M08400
• Forged construction for strength and heat resistance
• Requires cylinder boring to match oversize diameter
• Designed for two-stroke 700cc Yamaha watercraft engines

Fits These Machines

• for Yamaha Wave Runner III GP 700 1994
• for Yamaha Wave Runner III GP 700 1995
• for Yamaha Wave Runner III GP 700 1996
• for Yamaha Wave Runner III GP 700 1997

On-The-Job Use

• Top-end rebuilds where cylinder wear requires oversize boring
• Restoring compression on high-hour 700cc watercraft engines
• Cylinder cleanup after damage or scoring
• Piston replacement during a full engine refresh

Specs At A Glance

Good To Know

Q: Does this piston drop into a stock cylinder? A: No, this oversize piston requires the cylinder to be bored and honed to 84 mm before installation.

Q: Should oversize pistons be installed in matched sets? A: Yes, when boring a cylinder, matching pistons across the top end helps maintain balanced compression and smooth operation.

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