Stihl MS-250 chainsaw engine bogging down
My neighbor's Stihl chainsaw was bogging down so I said I'd take a look at it. It's not very old.
I took the carb off and dismantled it; blew out the jets, eyeballed everything. Checked the spark arrester, it's like new. Put in new gas mix. Chain spins freely. Adjusting screws at their proper position. Spark plug is new and proper type.
Went to start it up and it ran great. Revved it up and down and it had great high speed and smooth low to high speed acceleration. After about 30 seconds it was bogging down again. It has an external tank vent, and it is working well. Tried restarting and it starts easy enough, but just won't go from low to high speed. If I coax it, I may get it to high speed for one second and then it's bogging again. Tried adjusting the Low speed screw a little, but no good.
Any suggestions appreciated.