Measure the engine before you get to far into it. The EFCO just fits in the cowl. That is with a 1/4" thick intake manifold and a very thin muffler. The engine box on this model is 6 1/2" wide 2 1/2" back from the prop hub. 3 1/4" off the centerline is much narrower than almost any intake manifold and carb on a decent size engine. If you did not care, just cut a big hole in the side and let it hang out. They suggest a G-26 but, it needs to be canted to fit. The BUSA tech guy said guys are using G38s with success. That makes sense because the muffler is on the back of the jug like a Ryobi. Ryobi? Nope the plug would stick out through the dummy engine. I have a couple of Briggs 40cc 4-strokes. Way to big, they will not fit neat. Really a Saito FG-36 would be near perfection. Spendy too! But then again with all my time and sweat? If only I could fine one for cheap.

In hindsite I might have been happier with a model of something that used a rotary engine. Maybe a Sopwith pup? The wide front end an cowl makes fitting a normal, intake and exhaust on the sides, type engine much easiar to install.