The three horse motors have sleeve style bearings on the crank and they must use a heavier oil mixture in the gas than other motors with ball or needle bearings on the crank. 16:1 is preferred but they will survive on 24:1 if they are babied.
Agree 200 percent… The beauty of these older engines is that when in good shape and tuned correctly, they barely smoke at all, even at 16:1.