Bit beaten around this photo but it's a cracker. The bike is a Harley Model J which looks to have had every bit as hard a life as the photo itself. I genuinely would be at a total loss as for the location but for the fact that someone has written Kokopo, New Guinea April 1919 on the reverse.
Kokopo was part of 'German New Guinea' until the start of the First World War when in 1914 it quickly fell to Australian forces. Presumably these chaps in the photo are Aussie military.