Press Release from AMA: The following rule change was created through AMA Congress and approved by the AMA Board of Directors in October 2015. This rule will go into effect Jan. 1, 2017. Changes for the 2017 season are reflected in red, bold type. Items that are struck through will no longer be valid.
Chapter 1.1; Chapter A; Paragraph 6: The minimum age for amateur riders is 12.
In all events, a rider must be 14 or older to ride motorcycles above a 250cc. In motocross events, a rider must be 14 or older to ride a 250cc 4-stroke/2-stroke motorcycle. In motocross events, a rider must be 16 or older to ride a 450cc or above motorcycle.
Example: A racer who is 13 years old on the day of the event is not permitted to compete on a 250cc model motorcycle. A racer who is 15 years old on the day of the event is not permitted to compete on a 450cc model motorcycle.