After the overhaul of the piston assembly I used this saw to cut up three rather large downed trees, and some other work. However, now it is acting odd. Will start, sound fine, and work for a couple of minutes, until it gets warm. Then it loses power when cutting. No particular problem restarting. Good rpm until it starts to take a load. Replaced gas filter, cleaned air filter and replaced spark plug. No improvement. Seems like it is getting enough gas to run, but not cut. Suggestions/comments in kitchen English please - I'm mechanically disadvantaged.