804M06640 Wiseco Std Piston Kit for Yamaha YZ250X 2016-2024 66.40 mm

Wiseco Std Piston Kit for Yamaha YZ250X

This Wiseco standard bore piston kit, cross-referenced as 804M06640 with a 66.40 mm bore, is a complete top-end replacement assembly engineered for the Yamaha YZ250X two-stroke engine.

Overview

This Wiseco Std Piston Kit for Yamaha YZ250X delivers a direct-fit top-end rebuild solution for riders who demand consistent compression and reliability. The 66.40 mm standard bore piston kit for Yamaha YZ250X is built for trail and enduro riders running stock cylinder dimensions. Each Wiseco Std Piston Kit for Yamaha YZ250X ships with the piston, rings, pin, and clips needed to complete the job.

Built For Performance

• Forged high-silicon aluminum alloy construction for strength under high combustion loads
• Standard 66.40 mm bore size matches the OEM cylinder dimension without overboring
• Precision-machined ring grooves for consistent ring seal and compression
• Kit includes piston, rings, wrist pin, and circlips for a complete top-end refresh
• Thermal expansion characteristics tuned for two-stroke enduro duty cycles

Fits These Machines

• for Yamaha YZ250X 2016
• for Yamaha YZ250X 2017
• for Yamaha YZ250X 2018
• for Yamaha YZ250X 2019
• for Yamaha YZ250X 2020
• for Yamaha YZ250X 2021
• for Yamaha YZ250X 2022
• for Yamaha YZ250X 2023
• for Yamaha YZ250X 2024

On-The-Job Use

• Scheduled top-end rebuilds on high-hour YZ250X enduro machines
• Restoring lost compression after ring wear or piston scuffing
• Pre-season freshening before long trail or hare scramble events
• Replacing a seized or scored piston on a stock-bore cylinder

Specs At A Glance

Good To Know

Q: Does this kit require cylinder boring? A: No, this is a standard bore piston sized at 66.40 mm, so it installs into a stock-dimension cylinder without machining.

Q: What is included in the kit? A: The kit ships with the piston, ring set, wrist pin, and circlips, though you should verify the exact contents against your service manual before assembly.

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