An experimental army Harley XA 750 from 1942 is among the rare bikes being auctioned at Shannons Sydney Spring Classic Auction on October 21.
The bike is expected to fetch up to $22,000, but it is not the most valuable.
That honour goes to an unrestored 1914 Model 10F V-Twin with two-speed rear hub expected to fetch up to $28,000.
The bikes are part of a private collection assembled over more than 40 years and involved the vendor travelling around the world to visit motorcycle museums, private Harley-Davidson collections and meet enthusiasts to seek out rare machines.
His aim was to have a Harley of each kind and type from the earliest models.
A previous sale of nine machines from his collection attracted International interest at MotorEx in Sydney, with all selling at or above estimated prices after being offered with no reserve.
This time four of the 10 models are being offered with no reserve, so buyers could secure a bargain.
The Harley collection will also be offered along with another collection of 10 British and European bikes all with no reserve.
They include a 1956 Triumph Tiger T100 and a 1959 Trophy 500cc, both with alloy engines, a 1951 Triumph 5T 500 sprung hub model and a 1969 Trident with raygun pipes and twin leading shoe brakes.
The other British bikes are two Post-war Ariels – a 1948 Ariel 500cc Twin and a 1949 Ariel Red Hunter 500cc single – a 1971 Norton 750cc Fastback and a 1951 Royal Enfield Bullet 350c.
An Italian 1970 Moto Guzzi Ambassador 750cc and a German BMW R75/5 750 complete the bikes from this collection.