I've had success repairing string trimmers in the past, ususally just by cleaning the carb. Took on a trimmer that wouldn't run for a co-worker. Usual cleaning didn't help. Put in a new gastket kit (no needle valve)and at least got it to run past the full choke stage. Eased it to the half choke and it still stayed running, adjusted the idle screw way high and managed to to even ease it to keep running in the run position, but as soon as I try to advance the throttle it stalls, almost like it starves for gas. Trimmer is las than two years old. I'm stumped