4649M09200 Wiseco Std Piston Kit for Yamaha YZ400F WR400F 1998-2000 92mm 12.5:1

Wiseco Std Piston Kit for Yamaha YZ400F/WR400F

This Wiseco Standard Piston Kit for Yamaha YZ400F and WR400F models delivers a 92mm bore at a 12.5:1 compression ratio, with the 4649M09200 part number serving as the OEM cross-reference for this standard replacement piston.

Overview

This Wiseco Standard Piston Kit is a direct-fit engine rebuild component for Yamaha YZ400F and WR400F models from 1998 through 2000. The 92mm piston restores factory bore and compression at 12.5:1, making it the correct choice for a top-end refresh or rebuild. Riders and mechanics who need dependable OEM-spec replacement geometry will find this Wiseco piston kit matched to the original specifications.

Built For Performance

• 92mm standard bore diameter matching original cylinder dimensions
• 12.5:1 compression ratio for factory-equivalent combustion performance
• Wiseco forged piston construction for strength under high-rpm loads
• Part number 4649M09200 provides a verified OEM cross-reference
• Piston kit includes piston, rings, pin, and clips for a complete top-end install

Fits These Machines

• for Yamaha YZ400F, 1998-2000
• for Yamaha WR400F, 1998-2000

On-The-Job Use

• Top-end rebuilds on YZ400F motocross bikes
• Trail and enduro service on WR400F models
• Routine piston replacement at scheduled service intervals
• Restoration of a worn or scored cylinder bore back to standard size

Specs At A Glance

Good To Know

Q: Does this piston kit require any cylinder machining? A: No, the 92mm standard bore matches the original cylinder size, so it drops in without boring or honing to a larger dimension. Measure your cylinder for wear before installation to confirm it is within service limits.

Q: What compression does this kit produce compared to the stock piston? A: This kit runs a 12.5:1 compression ratio, which matches the original factory specification for the YZ400F and WR400F. Verify your head and valve condition before assembly to avoid detonation issues.

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