My first conversion was a Ryobi 31cc with the long shaft. All stock with the exception of a gutted muffler. It turned a 16 6-10 Zinger prop between 7200--7500 rpm. It flew my Ryan's Rebel at 14 lbs very good. It needed to be started with either a pull rope or an electric starter. I later built a Tim 6 ignition and am presently flying it with it. Now it hand starts very easily, and that was my reason for using the Tim 6, other than just seeing if I could make it work, and it works very well for me.