The problem is in the carburator.
You need to clean the carb thouroughly with spray carb & choke cleaner. You need to purchase a kit #631021B from a Tecumseh dealer.
When you take the fuel bowl off, notice about a half inch above the bottom of the pipe leading down into the bowl, there is a very small hole located in the threads that the bowl retaining plug was removed from. That hole is the Low Speed Jet and needs to be cleaned using a fine wire. I use a wire removed from a steel wire brush with a small bend about 1/4 inch from the end. Then use lots of carb cleaner in all the holes you see.
The neopreme seat where the inlet needle sits needs to be removed also. I insert a small screwdriver into the hole, taking care not to scrape the sides and give the old rubber seat a little twist, which loosenes it in the hole. Then a little shot of compressed air in the fuel inlet tube simply blows the old seat out. Use safety glasses & take care where you aim! The new seat has a little circle on one side and is smooth on the other. The side with the circle made into it goes into the hole first. It should come with an instruction sheet in the kit.
There is no vacuum advance or choke sensor on Tecumseh engines, so you don't need to worry about that.