I once contacted MTD about Troy Bilt engines and found out the engines are Ryobi engines,but that Homelite made them for Ryobi.That's why this one resembles the old Ryobi 31cc.I've had the Ryobi,Craftsman and Bolens 31cc trimmers and the engines were the same and all made in the same place for whatever company wanted to put their name on them.I now have a Troy Bilt 25cc 4 cycle TB6040XP that is made for MTD to put into their Troy Bilt trimmers.I sold the 31cc engines to guys that wanted to convert them to airplane or airboat engines,so it can be done. Jag Engines and Carr Precision make the mounts and other items that are needed to convert these engines. www.jagengines.com and www.carrprecision.com