I have a couple questions for you and it probably isn't this simple, but I overlook these things sometimes. 1.) Are you still running your old gas? 2.) Did you pull the plugs and check them? If the plugs are filled they motor will run ok but not great at full speed, but will idle really bad and stall. The only other thing that i can think of is that you might need to clean the carborator. If you take the plastic bowl off you should get an idea if that is the case. I have been fortunante to never really need a repair to my motor that i took it somewhere. If I were to take it somewhere it would probably be Richy in Franklin, PA.