40 C.F.R. § 205.157-3 Configuration identification.
Title 40 - Protection of Environment
(a) A separate vehicle configuration shall be determined by each combination of the following parameters: (1) Exhaust system (engine): (i) Mufflers; (ii) expansion chambers; (iii) spark arrestors; and (iv) other exhaust system components. (2) Air induction system (engine): (i) Intake muffler; (ii) intake ducting; and (iii) air cleaner element. (3) Vehicle drive train: (i) Chain; and (ii) shaft. (4) Transmission gear ratio: (i) Standard transmission; and (ii) automatic transmission. (5) Cooling system configuration: (i) Natural air cooled; (ii) liquid cooled; and (iii) forced air cooled. (6) Category parameters listed in §205.157–2. (b) [Reserved]
Title 40: Protection of Environment
PART 205—TRANSPORTATION EQUIPMENT NOISE EMISSION CONTROLS
Subpart D—Motorcycles
§ 205.157-3 Configuration identification.