MS261 won't restart once warmed up. (6-7yrs old unit)

[Scooter68]

Have a Stihl MS261 (not a "C-M" model) In the past few months it's become very difficult to use. Will start when cold (outside temps in the 80s-90s) using full choke with 5-6 pulls, then one or two pulls at 1.2 choke, but will not idle.

After warming up more than a 10-30 seconds it will not restart

Checked spark arrestor screen - perfectly clean
Gas used is always 91 octane non-ethanol
Cold weather 'shutter' solid side is in as per Stihl directions

Tried to do LA screw adjustment with about a 1/8 turn but still stalls out
Acts flooded (Strong gas smell)
Will restart after it sits for at least 45 - 60 mins but still won't idle

The carburetor H & L screws are covered with concave silver metal inserts.
From what I have read it appears to need a 2mm allen wrench in those openings (yes/No)
I cannot see the vent tube even after removing the cover and air filter - probably looking in the wrong place
Spark plug has been replaced once.

Total run time on this one is around 25-30 tanks full

About to take it to the shop but want to see if anyone has any ideas. Can take photos and send/attach if that would help.

My experience level is moderate. Over 70 yrs old started really using chain saws about 22 years ago. Started with some Craftsmen chainsaws because I did't want to tear up a really good chainsaw. Finally outgrew those as they just didn't do that well. Moved on to a Stihl MS 271 Farm Boss and after about 12-14 years finally made the terminal mistake of gas with no oil. That's when I bought the MS261. With 17+ acres that is about 60 woods I use a chainsaw multiple times a month for some project. I have a gas powered backpack blower (husquvarna) a Stihl weed wacker, a Stihl battery chainsaw and my milling chainsaw an MS362 >>> That sums up my chainsaw experience.<<<

 

[Bob Hedgecutter]

In my experience- if a saw will not hold tune- it has an air leak.
If you do not have the tooling to test, a shop can, but first off remove the muffler and show a photograph of the piston viewed through the exhaust port.
Try removing the spark plug, tip a teaspoon full of oil down the hole on top of the piston, swill it about a bit, replace the plug and try to cold start the saw as normal.

 

[Scooter68]

Cold Weather tab - OK just got the chainsaw back from shop. Have not tried it BUT I heard something that does NOT agree with what I keep reading on line. The cold tab has an open side and a closed side. Based on what I have heard and read the closed side should be in to block hot air from the cylinder head from flowing to the carb in HOT weather. The OPEN side should be in for COLD weather. Young guy as the shop appears to have it backwards. Going to reverse the tab as he had the OPEN side in allowing Hot Cylinder air into the carb. SHOUT OUT if I'm wrong - PLEASE.

 

[Bob Hedgecutter]

The shutter has the instructions molded into itself- with arrows and rather obvious weather condition emblems as to which way it goes.
Rather obviously, for winter running, snowflake emblem and arrow indicate the port is open to allow warmed air from around the cylinder to enter the airbox helping to prevent the carb from icing up.
However I very much doubt the shutters position has any bearing on your original complaints.