4976M07700 Wiseco Std Piston Kit for Yamaha YZ250F 2008-2011 77mm 14:1 CR

Std Piston Kit for Yamaha YZ250F

This Wiseco standard bore piston kit for Yamaha YZ250F delivers a 77mm forged piston with a 14:1 compression ratio, cross-referenced under part number 4976M07700.

Overview

This standard piston kit for Yamaha YZ250F restores top-end power in 2008-2011 four-stroke motocross engines. Each kit is built around a 77mm forged piston running a 14:1 compression ratio for strong, reliable combustion. Riders and rebuilders choose this piston kit for Yamaha YZ250F service when factory bore dimensions need to be maintained.

Built For Performance

• Forged aluminum construction for high strength under combustion loads
• 77mm standard bore diameter matches stock cylinder sizing
• 14:1 compression ratio for strong mid-range and top-end response
• Kit includes piston, rings, wrist pin, and circlips for a complete top-end refresh
• Cross-reference 4976M07700 for verified application matching
• Machined ring grooves for consistent ring seal and compression

Fits These Machines

• for Yamaha YZ250F 2008
• for Yamaha YZ250F 2009
• for Yamaha YZ250F 2010
• for Yamaha YZ250F 2011

On-The-Job Use

• Top-end rebuilds after piston wear or ring blow-by
• Routine motocross engine refresh at factory bore size
• Race engine assembly where stock bore rules apply
• Restoring compression on high-hour YZ250F engines

Specs At A Glance

Good To Know

Q: Does this kit include rings and pin? A: Yes, this piston kit ships with the piston, rings, wrist pin, and circlips needed for a standard top-end rebuild. Confirm bore condition and clearance before assembly.

Q: Can I install this without machining? A: This standard bore kit is designed to fit a stock-size cylinder in good condition. Measure the cylinder for wear and taper, and hone or replate as needed before fitting the new piston.

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