4854M06650 Wiseco .040 Piston 66.50mm 13.5:1 for Yamaha YZF-R6 YZF-R6S 2001-2005

Wiseco .040 Piston for Yamaha

This .040 overbore piston for Yamaha YZF-R6 and YZF-R6S engines replaces OEM part 4854M06650, measuring 66.50mm with a 13.5:1 compression ratio.

Overview

This Wiseco .040 piston for Yamaha YZF-R6 and YZF-R6S machines is a forged replacement piston for engine rebuilds and top-end work on 2001-2005 models. The .040 piston for Yamaha restores compression and bore geometry after cylinder work, making it a fit for riders and mechanics rebuilding worn top ends. Each .040 piston for Yamaha is sized to 66.50mm with a 13.5:1 compression ratio for the specified engine family.

Built For Performance

• 66.50mm bore size for .040 overbore applications
• 13.5:1 compression ratio for strong cylinder pressure
• Forged construction for strength under heat and load
• OEM cross-reference 4854M06650 for easy lookup
• Direct fitment for Yamaha YZF-R6 and YZF-R6S 2001-2005 engines

Fits These Machines

• for Yamaha YZF-R6 2001-2005
• for Yamaha YZF-R6S 2001-2005

On-The-Job Use

• Top-end rebuilds after cylinder boring or honing
• Restoring compression on high-mileage engines
• Race and track engine refreshes requiring overbore sizing
• Shop builds where OEM bore replacement is needed

Specs At A Glance

Good To Know

Q: Does this piston require cylinder boring? A: Yes, a .040 overbore piston needs the cylinder bored and honed to match 66.50mm before installation. Confirm your machine shop's final bore measurement against the piston spec.

Q: Is this an OEM Yamaha piston? A: No, this is an aftermarket piston cross-referenced to OEM number 4854M06650. Verify fitment against your engine before ordering.

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