Description
A worn or damaged piston directly throttles your PW50’s performance, causing compression loss, poor throttle response, and accelerated engine wear. The Wiseco PK1157 restores full compression integrity and thermal efficiency with precision-forged internals—essential whether you’re rebuilding after years of trail riding or optimizing an existing engine. This complete kit eliminates sourcing multiple components separately, giving you everything needed for a professional top-end rebuild in one box.
- Bore diameter: 40mm
- Material: Forged aluminum alloy
- Includes: Pistons, rings, wrist pin, circlips, gaskets
- Fitment: Yamaha PW50 (1981–2025)
- Installation: Bolt-on top-end replacement
- Heat-treated for thermal stability
- Optimized ring groove design
- OEM-equivalent precision tolerances
- Enhanced compression sealing






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