Check the exhaust port behind the muffler. See if its caked in black carbon. If it is take spark plug out, move piston as low as it will go. Carefully take a small flat head screw driver and scrape it out do not touch the piston. Take compressed If blow through the plug hole, then into the exhaust port, then again in the spark plug hole. Reassemble.
Next take the front panel off the muffler and check the screen for carbon build up if there is any use a wire brush to clean or just be rid of the thing if you wise.(I pull all mine out)
Still having a problem get a echo tune up lit $10 at homedepot comes with fuel filter, air filter, spark plug.
Still having issues carb is the issue and a model that old you might as well replace it. My list starts with the least expensive