Well, I got a free Echo cs-510 the other day. Didnt get a lot of info on it other than the previous owner had run it and it started running poorly so he put a carb kit in it and it ran fine again. Then I guess it up and quit on him. So, I got it, and began checking it out and after muffler removal I found the exhaust side of the piston to be mangled rather oddly. Anyway, I went ahead and tore it on down to see if the cylinder was ok (more or less to see if it was worth putting a new piston in). The cylinder is really good for the most part except it feels a little rough below the exhaust port (as you would expect after seeing the piston). Anyway I think it should clean up ok as my fingernail didnt catch on any of the scoring but I tossed in a picture so you guys can input you two cents if desired. But my real question is what happened to that piston!?!? Check out the pic and let me know what you think...I dont want to put this thing back together if it just going to do that again. Also I should note the intake side of the piston is perfect...no scoring at all. Thanks for the help in advance.