In 1990 Team Jean Stalaven decided to choose light weight over power for their entry into the Dakar. The choice fell on the single-cylinder engine Husqvarna 510, bored out to 570 cc.
The shell, designed by Michel Assis, However was revolutionary - It
was made up of two parts welded together in order to stiffen the whole
structure keeping it extremely slim and racy, unusual aesthetics against the
mastodons of the era. Result of the whole operation, an engine with around
sixty horses for 130 kg dry weight, and 185 kg fully loaded: against the 250 kg
of twins. A power-to-weight ratio definitely interesting on paper.
Unfortunately none of the three riders finished the race - Michel Merel,
Laurent Charbonnel and Luc Pagnon all DNF'd.
http://www.parisdakar.it/en/team-stalaven/