I don't understand the fuel consumption comments. My experience is totally the opposite. My little Saito 72 is one thirsty mutha. My Webra 1.20 just sips fuel. You have to compare fuel consumption based of static and dynamic thrust, and how well the engine behaves at part throttle settings. Since the venerable Saito mentioned above has gotten so much attention on this thread, I will submit that mine consumes about 0.8 oz per minute at mixed throttle settings including full, half, and quarter throttle. The airplane is a GP Extra .40 and I use a 13-6 prop. My Webra 1.20 consumes about 1.0 oz/ minute with a 16-8 propeller and an 11 pound airplane and identical flying style. It produces almost twice the thrust as the Saito. Other fellows at my field also complain about the fuel consumption of Saitos. On the other hand, there are about 20 OS FS91's at our field and they all get very good fuel economy. They run very nice too.

I best if you tested the Brake Specific Fuel Consumption of a population of 2 strokes vs 4 strokes, there would not be any statistically significant difference.

Oh, as a motorcyclist, the comments on this thread about them make me laugh.