Honestly, if your pole trimmer is more than four years old you would probably be money ahead if you were to buy a new carburetor. There are check valves in most two stroke carburetors and they can be damaged by carburetor cleaners. The check valves are usually located below the purge bulb and they look like tiny metal washers, in a plastic spacer plate sometimes, and are very difficult to replace.
The fuel lines also go bad from ethanol in the fuel and should be replaced if they are getting hard or discolored. I work on two stroke engines all the time and see this problem every day. A new carburetor, new fuel lines, new spark plug, new fuel filter, new air filter, clean the fuel system out and you should be good to go.
The fact that fuel mix is now shooting in the carburetor when you prime the system shows that there is a leak somewhere in the carburetor. Again, you'd be money and time ahead by replacing the carburetor.
Just my :2cents: