Small Engines (Lawn Mowers, etc.): repair homelite line trimmer, air filter foam, line trimmer

Question
I am trying to repair a Homelite line trimmer engine. It has on the tag: UC No. 20544C and Ser.No. HL0121399.

I had to get new primer bulb, tubing and end-line filter and return line tubing. I cleaned the plug and checked the spark with the plug held to the top of the engine. I tried starting it but didn't even get it fire at all. I tried a little gas in the carb and even tried a spurt of starting fluid. I thought it might be flooded so took the plug out again. It was wet so I disconnected the fuel line, took out the plug and let it air out. When I tried again I just sprayed very little starting fluid in the air filter foam and still not anything. Can you give me any more ideas to try?
Roy

Answer
Ok lets think this over. When you removed the plug to test for spark you stated, "with the plug held to the top of the engine", BUT, did you ground the base of the spark plug to the metal engine block as needed to check for spark? If you did, and had no spark, then you can dump a refinery full of gas, and a barrel of starting fluid in the air filter , and carburetor, but with out spark will never start. You said you checked the spark this way, but failed to say if you had a good blue spark. If your getting good spark, chances are your carburetor is in need of a rebuild, or a good cleaning due to either a diaphragm being worn, or dirt or such not allowing the float needle to seat correctly. It looks to be flooding so much there is just too much fuel to ignite. To cause ignition within the cylinder the fuel to air ratio must be just right, a good solid blue spark must be present, along with good compression, and correct ignition timing. If your failing to get a good spark chances are your ignition coil is faulty. Might also want to make sure your spark arrest on the exhaust side is not plug with carbon deposits, and the ports are clear of carbon.......Tm