Kempster earned the nickname 'Smiling Jim Kempster' and came to prominence in 1928 when he won a race against Roger Frogley, in a match deemed to be the English Championship. Kempster had raced against the early Australian pioneers. He earned significant prize money during 1928 and won an International title in front of 45,000 at the new
Wimbledon Stadium. Kempster was given the title of World Champion after the success because he had beaten the former title holder
Sprouts Elder, of the United States. He joined the
Wimbledon Dons for the inaugural speedway season in England. He soon became their club captain and finished fourth in the riders league averages during the
1929 Speedway Southern League despite the fact that Wimbledon finished bottom of the league. He captained England against Australia on 30 June 1930, for England's first test match. Kempster continued to ride in the
top tier of British Speedway from 1929 to 1933. He signed for
Clapton Saints in 1933. After retiring he coached novice riders at Luton and made a brief comeback for the
Wembley Lions during 1936 as a backup rider. ==Personal life==