Wiseco PK1903 Piston Kit Yamaha Compression - 2012-2013 YZ250F 14 1

The Wiseco PK1903 is a complete top-end piston kit designed for the 2012–2013 Yamaha YZ250F with a 14:1 compression ratio. This kit is engineered for riders who demand maximum performance and reliability from their four-stroke motocross engine, whether rebuilding a worn top end or overboring to the next oversize.

Wiseco pistons are manufactured using a forged aluminum construction, which delivers superior strength, reduced weight, and better heat dissipation compared to cast alternatives. The forging process aligns the grain structure of the metal, resulting in a piston that can withstand the high RPM and thermal demands of competitive motocross riding.

Kit Contents:

• Forged piston — high-strength aluminum construction for durability and performance
• Piston rings — precision-fit rings for optimal compression and reduced blow-by
• Wrist pin — hardened wrist pin for secure piston-to-rod connection
• Circlips — retaining clips to secure the wrist pin in place
• Top-end gasket set — all necessary gaskets for a complete top-end rebuild

Key Specifications:

• OEM Reference: 40094M
• Compression Ratio: 14:1
• Application: 2012–2013 Yamaha YZ250F

Wiseco is a trusted name in performance piston manufacturing with decades of experience supplying OEM and aftermarket components for motocross, off-road, and powersports applications. The PK1903 kit provides everything needed for a professional-quality top-end rebuild in one convenient package.