Well, I'm not sure when it happened to be honest. Took it to the dealer when I noticed a gas leak between the tank and carb. Had that, the tank vent, filter, carb kit, plug and retuned. Was gonna do the muffler mod deal and when I pulled the muff I noticed the piston. It idles week and is snappy. Doesn't seem to be down on power. It wears a 20" full chisel and I cut mostly hardwoods with it. I did some trading with the brother in law for it who originally purchased it from e-bay. So there's no telling what happened to it before him. He works for a tree service (I used to also) so I don't believe he hurt it. I didn't run it long after the gas leak was discovered either.