Had my Stihl MS391 up for sale on local CL and had a potential buyer look at it. He starts it on 3rd pull, removes choke and goes WFO on a stone cold motor. I shouted and he backed off the throttle. I always idle cold engines whether 2 or 4 stroke, so I just learned I've been doing it all wrong. He let her rip again and I yelled the saw was his now! Unbelievable that he tried to lowball me too. I got my asking price and an education! Reason why he was looking for a replacement for his MS391? You guessed it, scored piston!