I am convinced that these engines are best left as built EXCEPT that conversion to electronic ignition to save weight and improve timing control (advanced at high RPM, retarded for better/slower idle) and swapping to a larger carb and minimum restriction muffler to let it "breathe" better at high RPMs are worthwhile. The other, more sophisticated, mods can provide some performance improvements but can also result in a destroyed engine. If you want a "real screamer", maybe a Ryobi should not be your first choice. It IS a good, easy to convert engine that will perform very well for what it is, for a very good price...