was there much heavy industry in Oz 1920/30s ? did they gear up for the war effort?
I'm not sure that motorcycle manufacture would be 'heavy industry', they'd be light industrial ?
There was a thriving industry in the teens and 20s for taking JAP engines and slotting them into locally made frames and cycleparts.
Probably a dozen brands or more that made quite a number - well more than a mere one or 2.
And lots of engine types/gearboxes/frame lugs/cycleparts were involved in this sort of manufacture also.
There are pages and pages devoted to this in Rob Sawards A-Z of Ausatralian made motorcycles.
Much Australian industry was involved in the WW2 effort.
Many a car maker and other industries were making guns and tanks and trucks and ammo etc etc.
At the end of the war, Oz had the 4th largest airforce in the world.
Mostly spits and and mustangs and B17s etc as lend/lease imports, but many an engine was made/rebuilt locally.
We diverge ..
There's little evidence that Villiers engines were built into locally made frames though.
Photos of any such assembly are in very short supply - even from makers who were reputed to be doing this
Full imports seems to have become the norm in the 1930s and postwar ?