Wiseco PK1037 Honda CR Forged Piston Kit - XR/TRX400EX/TRX400X 85.50mm 11 1

The Wiseco PK1037 is a complete forged piston kit engineered specifically for Honda XR400R, TRX400EX Sportrax, and TRX400X engines. This kit delivers an 85.50mm bore (+0.50mm oversize) and an aggressive 11:1 compression ratio, making it an ideal choice for riders seeking a reliable, high-performance top-end rebuild.

What's Included:

• Forged high-performance piston — 85.50mm bore diameter
• High-performance piston ring set
• Alloy wrist pin
• Top-end gasket kit

Key Features:

• USA forged and machined — engineered, forged, and machined in Mentor, OH for consistent quality control across every stage of production
• Dedicated forging — each piston is a purpose-built forging for this specific engine application, not an adapted design, optimizing the strength-to-weight ratio
• Aerospace-grade alloy — utilizes high-strength aerospace alloy for superior durability and extended service life
• 11:1 compression ratio — raises compression over stock for improved throttle response and peak power output
• Race-ready dome finish — smooth dome edges promote improved combustion chamber flow for 4-stroke applications
• Superior to cast pistons — forged grain structure is aligned to part geometry, providing greater resistance to impact and fatigue compared to brittle cast alternatives
• Skirt coating — factory-applied skirt coating reduces friction and wear during break-in and normal operation

Wiseco's forged 4-stroke piston kits are built to the tightest tolerances, delivering the ultimate combination of performance and long-term reliability whether you're trail riding, racing, or completing a full top-end rebuild. Note: This product is not CARB legal and is not for sale in California.