Section 7J. The registrar, after a hearing, may make, amend or rescind, rules and regulations relative to handlebars on motorcycles operated in the commonwealth. A copy of such rules and regulations attested by the registrar shall be prima facie evidence that they have been made as provided by law. Whoever violates any rule or regulation made under the provisions of this section shall be punished by a fine of not more than twenty-five dollars for the first offense and not more than fifty dollars for a second or subsequent offense.