A curious accomplishment on an old British bike...this was posted by one of the Aussies on SR500 forum:
"In the early 80's I competed in a fuel ecomonony run with my local vintage bike club. Over a 110Km run I manage 83mpg (about 30km/L). The winner,Bill, on a 1950's Ariel 500 single achieved 175mpg!! I had done the following to reduce fuel usage: In the carbie went 2 size down on the pilot jet and dropped the needle to its lowest setting(raised the clip to it highest position). cleaned the chain (non oring) and lightly oiled plus inflated the tyres to about 60psi. Cleaned the wheel bearings of grease and oiled them with light weight oil. Pryed the disc pad away from the discs at the start and didn't use them until I had to stop at the finish. Rode the entire distance at about 60kph at a near constant throttle with out lugging / loading the engine. Bill on his Ariel, rode the bike as it came out of the shed, rode at normal pace about 50 - 55 mph!
CJ"