OK pro men. Thanks for equal time. I will talk about my limited experience on low line trimmers. Both 2 stroke 31cc. I sense and see a huge offering of "refurb" units, and can guess why. Perhaps average owners find the 2 stroke drill tiresome and confusing. By that I mean getting the oil-mix right and starting. The starting on both my 2 trimmers has been the same.
Ten bulb squeezes until the bulb feels full, choke in 1st position, about 3 pulls and the engine should cough "start," but not start. Do not continue pulling on position #1 or risk flooding-engine is primed rich and wants leaner charge. Move lever to position #2 and pull. My engines start then, 99/100 times without fail. Run engine in position 2 until warm enough to move choke level to position #3. Change lever from 2 to 3 while running.
If engine dies (esp. cold weather) go back to #1 position for 1 pull, then to pos #2 until starts. Run it another 20-30 seconds until position #3 can be selected. I think new owners get so frustrated with fouled plugs (many do not know what that is) they return the timmer. Hot engines should start immediately . Do not move choke lever from position #3. If engine is only warm and will not start, move to position #2, then #3 asap.
In seemingly hopeless starting cases put lever in #3 position and pull 5-8 times to purge over rich condition. Then start over.
First trimmer Ryobi, 2nd the Sears weed whacker. As usual I talk too much. Do not know if this applies to upscale units.
Sidenote: I found and used a great little plug by Autolite SE 2957 , bubble pak (also SE 2954). Plug has ?platinum? center electrode. Lasted many years. Disappeared from internet, but recently surfaced at an auto parts store for $.99. Get one.