The Echo engines we are using for twins, and now this amazing four cylinder job have a full crankshaft with bearings on each end. The Ryobi engines have a cantilever crank with bearings only on the front. I don't know how one would connect two Ryobi crankshafts and make it work, even if you solved the crankcase problem.

Super cool engine aviatorplus. Nice work!!

AV8TOR