Spending more time on this site i now understand CAD.
We have a MS661 that’s about 2 YO. Prolly run 3-5 tanks. Most recently run at Newnan GA tornado response last year. Recently went to help remove a 42 in poplar and it never popped. Checked plug and was dry. Certainly welcome thoughts on diagnostics or starting options. Obviously I’m not a saw mechanic. Pulling the cord on that saw a continuous 25-30 times at 66 is a bit different than at 56 … even w compression release. TIA
If that was the case on any saw, I would first check that the fuel metering needle is not stuck down inside the carb, sometimes, when all the mix dries out, the oil can stick things closed, inc some of the drillings/ passages inside the carb.
The fuel metering lever is what is attached to the fuel metering diaphragm, and regulates how much fuel is kept on that side of the carb, think fuel bowl and floats on a car carby (sorry I dont know your level of experience here, so sorry if its a bit basic).
Needle is part no1 on page 23 of the IPL attached.
The 661 carb is pretty much like a normal carb, but instead of a main jet/ mixture screws setup, its just electronically controlled by the fuel solenoid.
I would first look ahead of the solenoid to make sure the fuel filter is ok, but my gut would be to look inside the carb, and check the needle is not stuck.
simple clean with some fresh mix, and away you go.
Some fuel down the plug hole, and when it fires up, might be enough to lift the needle up and free it too.
But then expect it to possibly flood out, as the needle/ seat area wont be clean and provide a tight seal, leaving it for a few hrs might let the fuel mix dissolve the dried up oil, and it may come good, but I would give the carb a clean if it fires up with some fuel down the plug/ or intake.
hope these help too, there is a fault finding flow chart in the service manual too.
edited for clarity, morning coffee still to activate brain.