I have a Bolens BL-110 25 cc trimmer, 4 months old. I've used it 10 times. I tried to start it and could'nt. I took it to a small engine shop, the man set the black adjustment screw and it ran for 3/4 of an hour. Again I could not start it. He charged me $22.50 and said if I have more problems call Bolens, these have been a problem from day one. If I screw the adjust screw all the way down how many complete turn how many complete turns out should I set it to?