Wiseco 4857M07700 Forged Piston Kit Bore CR - 4-Stroke 77mm 13.5 1

The Wiseco 4857M07700 is a 4-Stroke Forged Series Piston Kit engineered specifically for the Yamaha YZF-R1 (2004–2006) five-valve engine. Featuring a domed piston crown, a 77.00mm bore, and a 13.5:1 compression ratio, this kit is built for riders who demand maximum performance and reliability from their top end.

Key Features:

• Forged aluminum construction delivers improved tensile strength over cast pistons, optimizing service life under high-stress conditions
• Application-specific forging designed and built for the YZF-R1 5-valve engine architecture for a precise, tight-tolerance fit
• Domed piston crown supports the elevated 13.5:1 compression ratio for enhanced combustion efficiency and throttle response
• Optimized strength-to-weight ratio via dedicated forgings, reducing reciprocating mass while maintaining structural integrity
• Complete kit includes forged piston, piston rings, wrist pin, and circlips — everything needed for a full top-end rebuild
• Engineered, forged, and machined in the USA at Wiseco's facility in Mentor, OH
• Note: Oversize bore applications require cylinder re-sleeving or boring

Wiseco's 4-Stroke Forged Series pistons are proven across every level of powersports riding, from street performance to track use. Part number 4857M07700 is a direct upgrade for the 2004–2006 Yamaha YZF-R1 and meets the demands of high-performance engine rebuilds.