Wiseco PK1357 Top End Piston Kit - 95mm 12.5 1 for YZ450F WR450F 2003-2005

The Wiseco PK1357 is a complete top end piston kit engineered for the 2003–2005 Yamaha YZ450F and WR450F. Featuring a 95.00mm (standard) bore and 12.5:1 compression ratio (piston number 4785M), this kit delivers everything needed to perform a thorough top end rebuild in a single purchase.

Wiseco pistons are produced exclusively using the forging process, starting with aerospace-grade aluminum alloy. Forging compresses and aligns the material's grain structure, resulting in a piston that offers superior tensile strength, impact resistance, and fatigue life compared to cast alternatives. Each piston features a dedicated forging specific to this engine application, optimizing the strength-to-weight ratio for both performance and reliability.

Kit Contents:

• Forged aerospace alloy piston (4785M, 95.00mm)
• High-performance piston ring set for extended service life and sustained power
• High-quality alloy wrist pin — precision machined for reduced friction and consistent durability
• Circlips
• Wiseco top end gasket kit — premium materials exceeding OEM sealing standards
• Top end needle bearing (where applicable)

Key Features:

• Forged aerospace alloy construction — superior strength-to-weight ratio vs. OEM cast pistons
• Dedicated forging per application — engineered specifically for the YZ/WR450F engine architecture
• CNC machined — precision tolerances for optimal cam shape and profile, maximizing peak horsepower and service life
• Race-proven design — trusted by professional race teams across all forms of motorsport
• Complete top end gasket kit included — premium materials exceed OEM sealing standards

The Wiseco PK1357 is the ideal solution for a performance rebuild or routine top end replacement on the 2003–2005 YZ450F and WR450F, providing race-level reliability and power straight out of the box.