[3] Karl Büsser made his debut in national and international sidecarcross in 1974 on the side of Ernst Ruegg, whose passenger he would remain until the end of the 1980 season.

In between, Büsser raced for one Grand Prix in 1979 with German driver Reinhard Böhler who would become the first-ever World Champion in the sport the following year.

[1] In the Swiss national championship between 1974 and 1978 the team generally finished between places three and six.

[3] In 1981 Karl Büsser joined the team of Emil Bollhalder and, with his new driver, had much greater success than before.

[1] After their double World Championship Karl Büsser retired from national and international competition at the end of the 1983 season, as did Emil Bollhalder.