1910 Silent Grey Fellow

 The 1910 Silent Grey Fellow is one of the last Harley Davidson single cylinder motorcycles with any sales success before the iconic V-twin emerged as the quintessential engine of the American motorcycle industry. Originally a 440cc engine, these were later enlarged to 564cc. These motorcycles were named for the grey paint and the quiet reliable engine and were one of the motorcycles that cemented Harley's reputation as a major manufacturer.
If you can't afford one  for yourself you can always build one. Check out: http://thekneeslider.com/honda-50-powered-vintage-bicycle-project/