Born August 1942, Andersson became the three year consecutive champion in the domestic 250cc class from 1966, and in 1969 signed up with the Yamaha Importer Team. He competed in the World GP on a modified version of Yamaha's production racer, and achieved a ranking of 8th in the GP250 of 1968. After the Yamaha Factory Team left the sport in 1969, Andersson finished 2nd after battling for the championship with Benelli's Kel Carruthers. From 1971, Andersson raced on the newly developed 2-cylinder, 125cc machine (YZ623→0W15), with which he added the 1973 and 1974 GP125 Championships to his collection. At 179cm and 63kg, the slim and tall Andersson used his free riding style and white racing suit that became his trademark, for with which he was nicknamed the "Swedish Snowman."
|Year||Class||Result & Pole position||Machine|
|1972||125cc||2nd||PP: 0||1st: 3||2nd: 1||3rd: 4||YZ623|
|1973||125cc||Champion||PP: 0||1st: 5||2nd: 2||3rd: 0||YZR125(0W15)|
|1974||125cc||Champion||PP: 3||1st: 5||2nd: 2||3rd: 1||YZR125(0W15)|
|1975||125cc||3rd||PP: 1||1st: 1||2nd: 2||3rd: 2||YZR125(0W15)|
*Results for years with a Yamaha factory team, riding a Yamaha factory machine or ranked 5th or higher riding a Yamaha production racer (World GP, World F750)