Wiseco PK1434 102mm 9.9:1 Forged ATV Piston Kit – Yamaha YFM660

The Wiseco PK1434 is a high-performance forged piston kit designed for the Yamaha YFM660 ATV engine, featuring a 102.0mm bore and 9.9:1 compression ratio. This kit includes the top-end gasket set, giving you everything needed for a complete top-end rebuild.

Wiseco forges all of its pistons in-house at its USA facility, maintaining full control over every stage of manufacturing — from raw bar stock to final skirt coating. This vertically integrated process ensures consistent quality and dimensional accuracy across every part produced.

Key Features:

• 102.0mm Bore Diameter – Precision-forged to exacting tolerances for optimal ring seal and longevity
• 9.9:1 Compression Ratio – Optimized for strong power delivery in performance and trail riding applications
• USA Forged Construction – All pistons forged in-house for superior grain structure and mechanical strength
• Top-End Gasket Kit Included – Complete kit for a full top-end service
• Skirt Coating Applied – Reduces friction and improves wear resistance during break-in and beyond
• High Strength-to-Weight Ratio – Forging process aligns grain structure to part geometry, maximizing impact and fatigue resistance
• Manufacturer Part Number (MPN): PK1434 | Piston Part Number: 4966M

Unlike cast pistons, which can fail suddenly when yield strength is exceeded, Wiseco forged pistons feature a condensed, aligned grain structure that provides superior resistance to impact, heat, and fatigue — making them the ideal choice for demanding ATV performance applications. Wiseco's in-house dyno testing and continuous R&D program ensure these pistons reflect the latest in piston technology, including advanced shapes and surface treatments.