Judging from the bicycles in the background, your grandfather was a resident of the USA at the time of the photo.
As R points out, the bike is a Henderson four - in fact the "streamliner" which was the last of the breed and only made from 1929 into early 1931 when the depression called things to a halt. The huge X on the tank transfer is a reminder that through the 1920s the Henderson name was owned by Schwinn's Excelsior company.
A truly fabulous vintage motorcycle - thanks for posting!
Leon