Wiseco PK1361 Forged Piston Kit with Top-End Gasket Kit - 95mm 13.5 1 for YZ/WR450F

The Wiseco PK1361 is a complete top-end piston kit engineered for the 2003–2005 Yamaha YZ450F and WR450F. Featuring a 95.00mm bore and an aggressive 13.5:1 compression ratio, this kit is purpose-built for demanding off-road and motocross applications where reliability and peak performance are non-negotiable.

Key Features:

• Forged aerospace-alloy construction — dedicated forging provides a superior strength-to-weight ratio and improved tensile strength over cast alternatives
• ArmorGlide skirt coating — reduces friction and noise while allowing tighter bore fitment for better ring seal and increased horsepower
• Race-ready dome finish — smooth edges promote optimized combustion flow for 4-stroke performance
• Engineered and manufactured in the USA — forged, machined, and assembled in Mentor, OH with full in-house process control from raw material to finished part
• In-house dyno development — Wiseco's dyno testing program validates piston shape, coating, and component performance before release
• Complete kit contents — includes forged piston, high-performance ring set, alloy wrist pin, circlips, and a full top-end gasket kit

Unlike cast pistons, Wiseco's forged units feature condensed, aligned grain structure that delivers higher mechanical properties, impact resistance, and fatigue life — critical qualities for sustained performance in Supercross, Motocross, and GNCC competition. The PK1361 uses forging number 4786M and is designed to exact OEM tolerances for a precise, reliable fit.

Important Notes: Any bore size other than stock requires cylinder boring and appropriate Nikasil plating or a new cylinder sleeve. High-compression ratios up to 13.5:1 require premium pump fuel. Always inspect and measure your cylinder before ordering.