Pistons fail for a reason. The common ones are cooling loss, wrong fuel timing, dirt past the air filter, and oil that no longer protects the skirt.
Patterns and what they suggest
- Scuffing on the skirt: oil supply, oil grade, or overheating
- Eroded crown edge: injector spray or timing
- A hole in one piston: that cylinder ran lean or detonated
- Even wear across the set: hours and maintenance, not a single bad part
When you open an engine, measure liners and check ring end gap. A new piston in a worn liner will not seal. Also inspect the cooling jets. A blocked jet cooks one piston while the others look fine.
Order pistons against the engine serial. Crown shape and ring packs change between arrangements, even inside the same series.