The G231 is not a converted airplane engine, Zenoah is producing a PUH version of the 231. They are still new, and Horizon is the US distributor.

The cylinder/piston design is different as is the carburetor. I have not done any port measurements.

The engine has fairly robust fins and runs about 80-100 degrees cooler than a normal G23. Thats about the same difference found with some of the aftermarket cylinders, so there isn't any reason to install them for cooling purposes.

Its easier to start than the G23 and it runs smoother than the G26 (at least over 10K RPMs). Not sure about actual power, but from some of the tests we've run, it appears to produce more torque than the G23.