677M06900 Wiseco .040 Piston Kit for Yamaha YZ250 WR250 1992-1998 69.00 mm

Wiseco .040 Piston Kit for Yamaha YZ250 & WR250

This Wiseco .040 overbore piston kit (part 677M06900, 69.00 mm) is a forged piston assembly that restores compression, seals the combustion chamber, and transfers power in 1992-1998 Yamaha YZ250 and WR250 two-stroke engines. It is made for riders who are rebuilding a worn top end or boring the cylinder to the next oversize. The .040 piston kit delivers the durability and consistent fit that high-revving motocross and off-road engines demand.

Overview

Forged from high-strength aluminum alloy, this Wiseco .040 piston kit is engineered to handle the heat and stress of two-stroke operation. It serves riders and mechanics rebuilding 1992-1998 Yamaha YZ250 and WR250 machines that need a fresh bore. Each kit includes the piston and supporting components required for the .040 oversize installation.

Built For Performance

• Forged piston construction for high strength and heat resistance under two-stroke loads
• Precision machined to a 69.00 mm oversize diameter for a true cylinder fit
• Designed to restore compression and combustion sealing in worn top ends
• Oversize bore matches cylinders machined to the .040 step
• Kit format supplies the parts needed for a complete piston replacement

Fits These Machines

• for Yamaha YZ250, 1992-1998
• for Yamaha WR250, 1992-1998

On-The-Job Use

• Top-end rebuilds on 1992-1998 Yamaha YZ250 and WR250 two-strokes
• Cylinder boring and honing jobs that use a .040 oversize piston
• Motocross and off-road engine refresh programs
• Race engine builds needing a fresh, true-bore top end

Specs At A Glance

Good To Know

Q: Will this piston fit a standard-bore cylinder? A: No, this is a .040 oversize piston and requires the cylinder to be bored and honed to match the 69.00 mm diameter. Always confirm your intended bore size before ordering.

Q: Does the kit include rings and a pin? A: The kit is a Wiseco piston assembly built for the .040 oversize application. Review the listing contents or contact us to confirm exactly which components ship with this specific kit.

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