(a) Any system installed on or incorporated in a new motorcycle to enable such vehicle to conform to standards imposed by this subpart:

(1) Shall not in its operation or function cause the emission into the ambient air of any noxious or toxic substance that would not be emitted in the operation of such vehicle without such system, except as specifically permitted by regulation; and

(2) Shall not in its operation, function, or malfunction result in any unsafe condition endangering the motorcycle, its rider(s), or persons or property in close proximity to the vehicle.

(b) Every manufacturer of new motorcycles subject to any of the standards imposed by this subpart shall, prior to taking any of the actions specified in section 203(a)(1) of the Act, test or cause to be tested motorcycles in accordance with good engineering practice to ascertain that such test vehicles will meet the requirements of this section for the useful life of the vehicle.

(c) If a new motorcycle is designed to require manual adjustment to compensate for changing altitude, the manufacturer must include the appropriate instructions in the application for certification. EPA will review the instructions to ensure that properly adjusted motorcycles will meet emission standards at both low altitude and high altitude.

(d) An action to install parts, modify engines, or perform other adjustments to compensate for changing altitude is not prohibited under 42 U.S.C. 7522 as long as it is done consistent with the manufacturer's instructions.