Wiseco PK1433 YFM660 Forged Piston Kit 101.0mm 9.9:1 Compression Ratio

The Wiseco PK1433 is a high-performance forged piston kit designed for the Yamaha YFM660, featuring a 101.0mm bore diameter and a 9.9:1 compression ratio. Manufactured entirely in-house in the USA, this kit (Wiseco piston number 4966M) delivers the strength and precision demanded by high-output ATV engines.

Wiseco's fully integrated manufacturing process — from raw bar stock through skirt coating — ensures uncompromising quality control at every stage. All forge tooling is produced in-house, and in-house dyno testing drives continuous development of advanced piston shapes, coatings, and components.

Why Forged vs. Cast?

Wiseco forged pistons offer a significant advantage over cast alternatives. Castings are typically brittle, lack defined grain structure, and are prone to catastrophic failure when material yield strength is exceeded. Forgings feature a condensed, feature-aligned grain structure that delivers superior mechanical properties, impact resistance, and fatigue resistance — exactly what high-performance motorsport applications demand.

Key Features:

• Bore Size: 101.0mm
• Compression Ratio: 9.9:1
• Piston Number: 4966M
• USA-forged construction for maximum strength-to-weight ratio
• In-house skirt coating for reduced friction and improved wear resistance
• Optimized piston design developed through in-house dyno testing
• Includes top-end gasket kit
• Compatible with Yamaha YFM660 ATV applications

Wiseco's PK1433 piston kit is the trusted choice for riders who demand reliable power and durability from their Yamaha YFM660 engine build.