Wiseco PK1003 66.5mm Forged Piston Kit with Top-End Gasket Kit Honda 185 200 ATC 10.25:1

The Wiseco PK1003 is a complete top-end piston kit engineered for Honda 185 and 200 ATC engines. Featuring a 66.5mm bore and a performance-tuned 10.25:1 compression ratio, this kit delivers a direct upgrade over standard cast pistons and includes a full top-end gasket kit for a complete rebuild.

At the core of this kit is a forged aluminum piston — a significant advantage over cast alternatives. Wiseco's forging process produces a dense, aligned grain structure that results in superior mechanical strength, improved impact resistance, and enhanced fatigue life. Cast pistons, by contrast, lack this grain structure and are prone to catastrophic failure under high stress. Wiseco forgings are designed to optimize the strength-to-weight ratio for maximum performance without unnecessary mass.

Wiseco manufactures all pistons and forge tooling in-house in the USA, giving them complete control over the production process from raw aluminum billet to skirt-coated finished parts. Each piston receives a diamond-turned finish from CNC machining centers, ensuring a precise bore diameter with zero size variation. ArmorGlide skirt coating is applied to 4-stroke race pistons to reduce friction and noise, contributing to increased power output and extended component life.

Kit Includes:

• Forged aluminum piston (66.5mm / 4156M bore)
• High-performance piston rings
• Alloy wrist pin
• Circlips
• Complete top-end gasket kit

Key Specifications:

• Bore Diameter: 66.5mm
• Compression Ratio: 10.25:1
• Piston Forging Code: 4156M
• Material: High-silicon, low-expansion forged aluminum

Wiseco has been at the forefront of powersports piston development for over 75 years, with a proven track record across Supercross, Motocross, GNCC, WORCS, and Snowcross competition. The PK1003 brings that same race-proven engineering to Honda ATC 185 and 200 rebuilds.