What motorcycles were used during World War II?

The BMW R71s and the R75s/An R75: were arguably the best bikes of the war. So successful were these that the Allies copied them both,just like the stahlhelm and the Jerry can.

The British army tended to make use of side-valved, single-cylinder Nortons and BSAs. This Norton 16H is typical:

US Army tended to use HDs - especially the WLA (note the holster for a Thompson machine gun, on the fork leg

Some Indians were also used, such as the 741. This is a 741, or 'Scout 500':

For the Germans, Zündapp made the KS 750 - that iconic flat twin motorcycle-sidecar

Ukranian-made KMZ 'Dnepr', motorcycle and side car, made to this day, in Kiev, which derives much from the German design.

The U.S. troops used Harley Davidson bikes in large numbers. The British used military bikes with and without sidecar made by Norton, BSA, Ariel and Matchless. France, Russia and China copied the BMW motorbike concept with flat twin engine and cardanic drive, but they started production not before the end of the war.

Royal Enfield WD/J2 A 500cc motocycle. Used by despatch riders.

Royal Enfield WD/RE "Flying Flea"A 125cc motorcycle that could be parachuted into the field.