Yes there are some small 4 strokes for edge trimmers they have been converted but they are still heavy. My brother has a os 160 4 stroke twin converted to spark and runing on naptha and 10% glow fuel. I have converted a 42cc pulan chansaw engine not an eazy conversion, also have converted a 25cc homelite trimmer and a ryobi 28cc. i am going to convert a 31cc for a giant stick I will build in the winter. i guess if you are looking for a 4 stroke sound but you won't find anything over a 30cc, not until they convert chainsaws. If you are interested this is my video of a ultraspadstick with a 28cc ryobi converted i made allmost everything my self from my broken edge trimmer. Most of the money was spent from wacker engines for parts for the conversion hear is the link. http://www.youtube.com/watch?v=W1dHMmcR92o enjoy