You'd have to ask the factory engineers of the time that one!
Keep in mind also, that there were these early rotary valve Australian engined Popes, and a later 1970's on 2-stroke series that used a Japanese Fuji Robin engine. Totally different beasts.
The early Victa mix was actually 24:1 [1/3 pint Castrol XL to 1 gallon of Standard grade petrol], and quite a few 1950's Villiers [e.g. the Midget series] ran 16:1.
As did many of the earlier chain saws, up to the Mono [US] sourced Mobilco saws that were still [though only just] on the market in the early 1970's. Primitive beasts, those things!
