Career
In 1980, he switched to Yamaha to contest the 500cc motocross world championship. He finished 3rd in 1981 and 1982. In 1983, he battled against Honda teammates André Malherbe and Graham Noyce to claim the 500cc world championship, on a Yamaha.
In 1984, an injury stopped Carlqvist from contesting the title again.
He raced for Yamaha until end of 1986. He continued the 500 GPs in 1987 and 1988 with a privateer Kawasaki KX500.
His last Grand Prix victory was the Belgian Grand Prix at Namur in 1988.