With direct cylinder injection, such as is now offered in some automobile engines, two strokes can run as clean as four strokes and make similar gas mileage too. They are inherently lighter, being bereft of valve train.
Given the static method by which displacement is computed, a two stroke will always have superior volumetric efficiency, compared to a four stroke.
If science, instead of politics, ruled racing, then the two strokes would still hold 100% of the spots on the FIM/MotoGP grid. We would likely have plain bearing lower ends with top ends fed by piston ports blowing supercharged air into cylinders fed fuel by post exhaust port closing high pressure direct injection. That said, an expansion chamber IS a supercharger, except, simply stated, it sucks instead of blows.
