adjust it back to the factory settings then go from there. i'm not sure what they are on a .15, but i'm sure you can find them. if you don't know them, ask the person you bought it from. but i can tell you if it's starting but only runs for a short time, then it has to be fuel or plug. make sure you have no air leaks from the head (in other words, check all your head bolts), check your backplate (inside of pull start), plug tight, all needles are seated in your carb. also check the o ring on the carb. i know it's a lot to do, but it has to be one of them. ... hopefully.