Hi Captin!!! The trimmer engine is a 31CC Ryobi Hybrid engine, it comes with 2 rings and dual ports on both sides, has a lot of compression but the exhaust timing was short at about 120 degrees of duration but I increased to 140 degrees, I already have it mounted and flying on a plane of my own design based on the application of a Ryobi engine, but let me tell you this engine makes this plane "TEAR" the sky on Glow/Gasoline fuel with glow plug, I'm having a ball with it and can't wait for the weekend to be here so I can go and fly again, At the time don't have a Tachometer to tach it by I guess it's over the 8000 rpm range with an APC 18x6W prop, I am realy happy with the end product and it only cost me $39.99 plus tax!!!! can you believe that???? keep in touch.
Your Buddy from down Baja Mexico Aero Nut.