Without looking like a complete plagorist here's an extract from Wikipedia's definition of a Cafe Racer...
"A Cafe racer, pronounced "Kaff " racer, is a type of motorcycle as well as a type of motorcyclist and have their roots in the 1960s British group the Rockers or Ton-up Boys. Rockers were a young and rebellious Rock'n'Roll counterculture that wanted a fast, personalised and distinctive bike to travel between transport cafés along the newly built arterial motorways in and around British towns and cities. The goal of many was to be able to reach 100 miles per hour, or "the ton".
Riders would strip down factory produced bikes, removing unnecessary parts and uprating the engines. The bikes looked raw and stripped-down while the engines were tuned for maximum top speed.
Because speed was valued more than comfort, bikes were fit with single seats, low handle bars, such as ace bars or even one sided clip-ons mounted directly onto the front forks for more precise control and to escape the wind. Distinctive half or sometimes full race fairings, large, hand-made, aluminum racing petrol/gas tanks were frequenltly left unpainted. Swept back exhausts and rearset footpegs were used to give better clearance whilst leaning through corners at speed.
These motorcycles were lean, light and handle road surfaces well...". You can read the entire article here.
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