Wiseco PK1384 Forged Piston Kit CR - 77mm 13.5 1 YZ250F WR250F 2005-2007

The Wiseco PK1384 is a high-performance forged piston kit engineered specifically for the 2005–2007 Yamaha YZ250F and WR250F. Featuring a 77.00mm bore and an aggressive 13.5:1 compression ratio, this kit delivers the power and reliability demanded by serious dirt bike riders and racers.

Key Features:

• Forged in the USA — engineered, forged, and machined in Mentor, OH for strict quality control from raw bar to finished part
• 77.00mm bore diameter with 13.5:1 compression ratio for increased power output
• Aerospace-grade aluminum alloy construction — high-silicon, low-expansion alloy provides superior strength, reduced weight, improved heat transfer, and extended service life
• Dedicated forging design — condensed, aligned grain structure optimizes strength-to-weight ratio and resistance to impact and fatigue
• ArmorGlide skirt coating — reduces friction and noise, allows tighter bore fit for improved ring seal and reduced piston rock, contributing to increased horsepower
• Kit includes: forged piston, high-performance ring set, alloy wrist pin, and circlips
• Top-end gasket kit included — everything needed to complete a proper top-end rebuild
• Compatible with cast iron, chrome, Nikasil, and boron composite cylinder bore compositions

Forged pistons outperform cast alternatives by offering a denser grain structure that resists catastrophic failure under extreme stress — a critical advantage in high-compression, high-RPM race applications. The PK1384 is built to withstand the abuse of competitive motocross and off-road riding while maintaining tight tolerances for consistent performance rebuild after rebuild.