I have now got my grubby little hands on a ryobi. Striped all the weedeater stuff off an made it look alot like a model airplane engine..How can I tell which one I have (28 or 31cc)?..I pulled the flywheel an magneto off an found that it has a real short shaft with a tapper down to the threads. An a really small half moon key(this mean short shaft?). It has a really tinny walbro-324 carb with no choke. I need one with a choke, so what would be a good replacement? I pulled the backplate off an noticed it was very clean on the inside, How ever the conecting rod looks like two chunks of flat steel pressed to one another. Don't look like a real strong setup.Is there a rod replacement that people are using when converting from yard tool to rc?....This engine is perfect with the rear carb an ext.It also looks like one of the Bennett deflector/muffler for a G-38 might work.Will it? Can't wait to get this thing converted an installed on a Great planes RV-4.......One more thing...If you can still see the cross hatchet hone on the cylinder does it need a new ring? Or is it still pretty fresh?