8. 1957 Triumph TRW
Source: Steve Munro, Flickr
The 1957 Triumph TRW had a very specific use when requested by the British army. For starters, it had to be able to afford at least 15 inches of water. Beyond that, it needed to be inaudible at a range of up to a half mile. So, the 500 cc side valve flathead prototype was first developed in 1942. Further years saw slight modifications and spec requests into your hand as the 1957 Drive which was competitive, a pleasure to ride and weighed right at 320 pounds. They were used by the British Army Royal Court of Signals until 1969. The chain driven four speed beast could produce 618.8 hp at 5000 RPM’s.