You may ask to exempt custom-designed off-highway motorcycles that are substantially similar to highway motorcycles under the display exemption provisions of 40 CFR 86.407-78(c) . Motorcycles exempt under this provision are subject to the restrictions of 40 CFR 86.407-78(c) and are considered to be motor vehicles for the purposes of this part 1051.
40 C.F.R. §1051.640