I am working on a homelite 410 for my neighbor. When I recieved it it had broken fuel lines and had not been run in about 10 years. I put new fuel lines on it and it started right up, with a little fine tuning on the carb I had it running perfectly. I had shut it off and started it a couple of times and started to make a cut through a small board with it when the engine revved high like it was running lean, so I let off the throttle and it continued to scream with the throttle closed and then died. It would not start back up until I turned the choke on and open the low speed adjustment screws all the way out. It will run like that, but with the throttle closed it screams and if you open the throttle any it bogs out and dies. It will hit a few times on half choke, but will not continue to run. Is this problem an air leak or something else.