So some food for thought…if you haven’t tried adjusting the high speed jet then I would definitely do that. If you have…then I would suspect two main possibilities. First that engine compression is low, don’t remember if you tested compression or not? Second, I would check what I call the “last chance” filter inside the carb body under the diaphragm plate. It’s a micro mesh metal cup shape. I am not certain if this saw has that screen though as many of these saws have different carbs. I personally put a WT-194 in mine, as it has a larger bore diameter and the saw likes it. Back to the filter, it gets clogged over time if the tank filter ever fell off and previous owner ran it then micro saw dust makes it in. Many saws I’ve seen will idle beautiful but wont flow enough fuel when RPM goes up and very often this is the root cause.
I am sure others will bring up some other possibilities, because there are others, but this is what I check first because it is free, easy, and commonly a problem.