My next project once these flat twin/ flat four "twingles' are up and running, is to build a single cylinder Victa engine with a rotary valve inlet head only, with a 2 stroke type exhaust, with an exhaust driven valve.
That's really amazing as I never heard of the Allstate nor the DKWThe most common model of "Twingle" two stroke engines were the Allstate 175 and 250 cc motorcycles sold by Sears in the late 50's. Built by Steyr Pusch in Austria they were torquey but low revving bikes with good reliability. Just outclassed by the Japanese bikes of the 60's.
At the other end of the spectrum is the DKW 500 cc racer from the 30's. A twingle with a third "pumping" piston to increase air flow through the engine it gobbled fuel (alcohol, nitromethane, and ???), made lots of power and held it's own against BMW twins and the Norton singles in the FIM Grand Prix races! A marvel of engineering! Bill in Boulder CO
In fact DKW were the large parent company to AUDI, the now famous German car maker......and one of those which made up the 4 ring symbol for Auto Union, the actual name of the merged four companiesThat's really amazing as I never heard of the Allstate nor the DKW