Wiseco PK1438 102mm 9.9:1 Forged Piston Kit with Top-End Gaskets for Yamaha Grizzly/Rhino 660

The Wiseco PK1438 is a complete forged piston kit engineered for the Yamaha Grizzly and Rhino 660 ATV/UTV platform. Featuring a 102.00mm bore diameter and a 9.9:1 compression ratio, this kit delivers a precise, performance-oriented fit for stock displacement applications. The forging number for this application is 4966M.

Kit Includes:

• Forged aluminum piston
• Piston rings
• Wrist pin and circlips
• Complete top-end gasket kit

Key Features:

• 100% USA-forged construction — Wiseco is the only aftermarket piston manufacturer in the United States to forge all of its own pistons in-house, with all forge tooling produced at their own facility
• ArmorGlide skirt coating — reduces friction and improves break-in, extending piston and cylinder life
• Aerospace-grade aluminum alloy — the forging process compresses molecular grain structure, producing superior strength, ductility, and resistance to impact and fatigue compared to cast alternatives
• Optimized strength-to-weight ratio — dedicated forging designs and 3D finite element modeling ensure maximum performance with minimal mass
• Compatible with all cylinder bore compositions — cast iron, chrome, Nikasil, and boron composite cylinders
• Complete top-end rebuild solution — includes all critical gaskets needed for a full top-end service

Wiseco's fully integrated manufacturing process — from raw bar stock through skirt coating and in-house dyno validation — ensures every PK1438 kit meets the demands of high-performance ATV and UTV engines. Whether used in recreational trail riding or competitive off-road conditions, this kit provides the durability and consistency that only a true forged piston can deliver.