History and regulations
* July 8, 1949: first regulations
o length: up to 2.8 m
o width: up to 1 m
o height: up to 2 m
o engine displacement: up to 150 cc (4-stroke), up to 100 cc; (2-stroke)
* July 26, 1950: major changes
o length: up to 3 m
o width: up to 1.3 m
o displacement: up to 300 cc; (4-stroke), up to 200 cc; (2-stroke)
* August 16, 1951: minor changes
o displacement up to 360 cc; (4-stroke), up to 240 cc; (2 stroke)
* April 4, 1955: minor changes
o no further differentiation between 2-stroke and 4-stroke: all up to 360 cc
* January 1, 1976: major changes
o length: up to 3.2 m
o width: up to 1.4 m
o displacement: up to 550 cc
* January 1, 1984: medium changes
o length: up to 3.4 m
o displacement: up to 660 cc
* October 1, 1998: today's regulations
o length: 3.4 m or less
o width: 1.48 m or less
o height: 2 m or less
o displacement: up to 660 cc