Third pick is a little obscure, but I like it because it gathered up a bunch of ideas, made them work well and glorified them with success. It's the Benelli 250, which put together an aluminum dohc top end for cooler operation, cam drive by gears and (eventually) an oil cooler. It brought distinction to its makers and to engineer Giuseppe Benelli through the 1930s and '40s. When, after World War II, engineer Alfredo Drusiani suggested to Mondial that a "real" four-stroke would whip all the yapping 125cc two-strokes of the late 1940s, he was thinking of this Benelli. Subsequently, Mondial was 125cc World Champion in 1949, '50 and '51. When MV needed to up their 125's performance, they bought a Mondial, and Soichiro Honda took one back to Japan for study. That's quite a chain of creative disturbance for a little old 25-horsepower Benelli from the early 1930s.