Thanks!Sounds like just another case of damage from running a saw that was set too lean on the high speed mix. You really have to learn to tune the saw so that it has the 4-stroke burble at full throttle out of the wood and just barely cleans out as you start the cut. Unreliable things to go by are the number of turns out on the mixture screws, how much power you think it is making, setting the high rpm to some number with a tach, how well it starts and idles.
Set the H screw so rich that it burbles and runs slow and rough in the cut, stop the saw and turn the screw in a bit and make another cut, keep doing this until you reach the point where the engine just cleans out and runs nice and crisp in the cut. Stop there, should only take 4 o5 cuts to reach the sweet spot.