I used to be a foreign car tech, and so while I don't know this specific saw engine, it is like a great deal of other saw engines. If i could get my greasey mitts on this saw I could fix it in several hours for anything wrong with it, so long as parts were forth coming.
The ATV sealer used to wreck for ever any carbs they were applied to. Today there may be some ATV sealer made for fuel, but if there is I am not aware.
What ATV did was break down pretty fast and go into a jelled solution, which clogged internal passaways, and so bad no amount of soaking in real carb cleaner, and or blowing air thru these passages would get rid of the clog.
IMO to this day ATV is the very best way to trash a carb, and I don't care if it is down draft, side draft or up draft types.
The saw type flutter fuel pump gaskets just go on clean, and with all clean and dry parts and work just fine that way.
Any time air gets to the combustion chamber not passing in a metered way thru the carb, it is called a vacuum leak. This will have different effects, depending on where and what is wrong.
Classic vac leaks cause High RPM, Hunting RPM, where the engine will cycle high in RPM and then starve for fuel and drop to near stall and then go right back to high idle.
Saws are prone to leaks of air at the carb to engine base, what ever type it happens to be on make and modle, the crankcase seals, due to a 2 stroke needs air tight crank seals to run right. or other case related leaks, when the engine case is a split case, or the jug is loose.
Vac leaks in a 2 stroke will kill the engine dead pretty fast, so it is wise to discover these with WD-40, Propane, pressue testing the saw, or what ever methods most please a tech.
My prefered method is WD-40, but as of late I wonder if the WD-40 chemicals and compound have changed to a no burn set of chemicals.
Recently WD-40 won't seem to act as a fuel, which I find disturbing, since this was a main tool for me to discover vac leaks.
I am hopping the built in cans with a red wand are different in compounds over the old fashioned cans. If all WD-40 has changed, then my next best method is propane. I can't see where propane is, which I could with the wd...