Son just brought home a Stihl fs200 strimmer bought as a non runner. Spark OK Stripped carb & all looks fine diaphragms intact & look newish, needle valve OK, blew through jets, minimal fuel staining etc. Tank filter OK, fuel pipes fine, primer bulb good. End result : will fire & run for a second then stops. Carb is a Zama CQ with a single adjustment screw which has a left hand thread & a square end, rather than a tapered metering end. This was positioned 5 1/2 turns out fr