50:1 using any Stihl or Husqvarna oil is fine. That is what I use in my 031's. It is not your problem.
My bet is you left it with fuel in it for more than a month. If so, rebuild the carb, either a Walbro WA, or a Tillotson HU3C. If it is the WA, then you need a k10WAT kit (about $5 shipped on ebay). Either way, clean the carb and go from there.
My plan for cleaning carbs is as follows: Buy a bottle of carb cleaner. Dump half to 2/3 of the carb cleaner in my truck. Cut the top off the bottle. Take the carb apart and put the entire carb into the carb cleaner bottle. Leave it overnight. Remove carb from cleaner and blow it all out with compressed air. Reassemble the carb with new gaskets.
The ethanol that the idiot politicians mandate be in gasoline likely destroyed the metering gasket in the carb.