Via: suzuki cycles
"Matt Guzzetta, a companion to Don Vesco at the Don Vesco Products, decided to built the most fuel efficient motorcycle in the world. The year was 1981 and Matt's goal was to win the Craig Vetter's Economy Run high mileage contest, held on trafficked highway in California, USA, between San Luis Obisco and Laguna Seca Raceway by Monterey.
Matt Guzzetta called his bike the Project 200. His goal was to ride 200 US miles on a gallon of gasoline (1,175 l/100 km). There had been vehicles that had already achieved the goal gut not with a street-legal motorcycle with all the equipment required for riding on roads, light, flashers, rear mirrors and such.
It took Matt three months to build his machine. He used a single cylinder two-stroke engine of a Suzuki GN125 that was later modified with help from the famous trim expert, PopsYoshimura. But the first thing to do was to modify the transmission ratios to get most of every drop of fuel by letting the engine run on its most fuel efficient revs.Magazine article of Matt Guzzetta's and Don Vesco's project bike Published in Swedish Allt om MC, January 1983
According to a magazine article from early 1983 Pops Yoshimura was going to use ceramic and synthetic materials on some of the engine parts. Unfortunately I don't know what modifications were actually made to the engine. By the time the article was published, Matt Guzzetta had calculated that after the engine trim the bike could probably manage 260 miles per gallon (0,905 l/100 km), perhaps even 300 mpg (0,784 l/100 km)...
Now we know that the bike could not run that long with only a gallon of fuel. Pops Yoshimura had not touched the engine by the time Matt Guzzetta participated the High Mileage Contest. The result: 152,31 mpg (1,544 l/100 km).
Suzuki GN125 had quite small front brake drum before Matt modified it. It was replaced with a larger one to compensate the rear brake that was removed when Matt modified the rear wheel. Instead of the drum brake, Matt mounted a starting engine freewheeling system from a Suzuki GS1100 into the rear wheel. The system let the wheel spin freely (when riding downhill) it the chain rotated slower than the wheel, naturally to save fuel.
Matt Guzzetta told back in 1982 that although the High Mileage Suzuki can be ridden on the road, it is not a practical bike. It cannot be leaned that much in corners because of the shape of the aerodynamic fairing, that also makes the vehicle very sensitive for side wind.
— A powerful blow of wind could lift me and the bike in the air and throw us to the Ocean, Matt told in the interview.
— The reason why I am building this machine is to find out a way to get better fuel efficiency for motorcycles with the help of aerodynamics. We will learn from our experiences and use the knowledge on normal motorcycles when we are done, he continued.
Matt had already experimented with a Suzuki GS1000G shaftie. By building and mounting an aerodynamic fairing to it he managed to lower the fuel consumption by 22% on highway speed."