They do have a winter setting.Can’t remember if this saw has a winter valve on the carby, but if set to Winter and still warm will behave this way when saw gets hot.
https://www.manualslib.com/manual/1053906/Stihl-Ms-391.html?page=36
They do have a winter setting.Can’t remember if this saw has a winter valve on the carby, but if set to Winter and still warm will behave this way when saw gets hot.
Based on the description and the video... The saw may have had an issue when you bought it, like an air leak or mis-adjusted carburetor running too lean. Cutting bar buried in hardwood with a possibly dull chain finished it off.Just bought a used Stihl 391 on Craigslist for $400 w/ 20" bar and new chain. Looked ok, started ok, seller told a pretty good story. Bucked thru 4 or 5 30" dia American Elm logs, ran strong. Then it stalls while cutting. Starts right up on 1st pull, runs about 15 seconds, then stalls (sounds like the fuel system is leaning out). Shot a video, posted to YouTube, https://youtu.be/SKfB7qj-LQI .
Stalls out like clockwork every 15 seconds, starts right up on 1st pull, runs for 15 seconds. It is full of high-dollar pre-mix gas, opened/closed fuel tank to verify it was not a tank venting issue.
Question for the experienced Stihl users, is there any particular issue that the 391 is known for that may be causing this strange stalling issue? ie weak fuel pump desigh, known carburator issues, or even something in the electronic ignition?
I will troubleshoot this saw and post the fix to this forum.
Removing the spark screen will cause the engine to lean out. You need to verify that it is not TOO lean and properly tuned after the screen was removed. Also check to see if the limiter caps are still intact.Looked for the exhaust screen, but appears prev owner has already yanked it out (Pic #1).
Glad the new filter helped, not surprising, not sure how none of us thought of that LOL.
Oh haha sorry mate!I think 2 of us did suggest that
Many thanks Magra for bringing this "carb heater" feature to my attention! Inspected, found it was 1/2 open. In Galveston this heater definitely needs to be locked to Summer mode, the day engine was stalling the ambient air temp was 85 F.
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