I have a GMS 120 basically the same as the smaller engines. And the key to getting any little 2 stroke engine to run good is to make sure it is sealed. crankcase especially.. i bought mine on ebay for 50 bucks and when i got it it wouldn't hardly run at all. I took it apart and checked everything. and re sealed the crankcase and replaced the O ring for the carb. and put a gasket betwen the engine and muffler. And put a 4 stroke plug in it and now it screams. and will shut off upon throttle closing a great running engine once you get it sealed. the GMS and tower engine's are cheaply made and after they have been run and broke in they tend to develope leaks.. and wont tune properly Seal it real good and i'm sure there wont be any more problems this goes for the needles in the carb having a good seal as well.