Hasegawa and Tamiya make 1930s vintage Harley Davidson and BMWs respectively.
Technically the Harley is a Rikuo but they were made under license by Harley in the 30s and virtually identical.
They are both military models with sidecars but can be used without the sidecars if desired.
A search on the auction sites on 1/48 motorcycles will bring them up.
Schuco makes a number of 1/43 vintage motorcycles as well.
Pete