These are the now "Old Style" Ryobi engines. Several companies make complete conversion parts for these engines. You will need to cut the flywheel shroud off as these are not removable as the previous versions were. Looked for these the other day while at Home Dopey and they were sold out. Would like to find one as my Ryobi 31cc has two stuck screws for the flywheel shroud. Would be easier to buy a new one than grind the screw heads off!