I am fairly new to the conversion bug. Some of these guys have orders of magnitude more experience than I. Maybe I am off base here. After doing some research my first step in the conversion hobby was to buy a quality ignition module. I have never done an engine that uses a flywheel. Weight, vibration, RFI, needing a starter, rough idle and performance compramises are things I have never had an issue with because I simply never use the stock ignition. I have an ignition for my test stand and I buy a new one for each plane. I bought a bunch of hall sensors and hundred pack of magnents. I make what I need for each project. Oh, my Ryobi runs real smooth and idles great. The top end figures are respectable. I did no internal mods other than bending the reed valve stop open a bit and chucking the jug gasket. I did make an open exhaust. I also buy new old stock carbs off of EBAY. Get some 11.1 and 13.49mm walbros with the accelerator pumps, about $10 each. Why fuss with questionalbe old carbs? These two sizes will cover most of the conversion needs. Even little engines (20cc) will run well with a 13.49 if you adust it properly. My little 20cc Stihl spins a 14x8 APC at 9500. The small carbs will be more foregiving though. I put a 13.49 on my Ryobi. I would loost the stock muffler on tht Ryobi and make something like what I attached. Make a can out of the bottom of an old fire extenguisher. Make the lid out of a piece of 1/8" flat stock with a shoulder turned to fit the inside of the can. The pipe can be a weed wacker handle or shaft and aluminum soldered in place. Use a draw bolt in the center to hold it togeher.