N.J. Stat. § 39:3C-8
The number assigned to a snowmobile, all-terrain vehicle, or dirt bike and required to be displayed pursuant to section 3 of P.L. 1973, c.307 (C.39:3C-3) shall be displayed on the snowmobile, all-terrain vehicle, or dirt bike at all times in such manner as the chief administrator may, by regulation, prescribe. No number other than the number assigned by the chief administrator, or a comparable identification number of the snowmobile, all-terrain vehicle, or dirt bike properly registered in another state, shall be painted, attached, or otherwise displayed on either side of the cowling, except that racing numbers on a snowmobile, all-terrain vehicle, or dirt bike being operated in prearranged organized special events may be temporarily displayed for the duration of the race.
N.J.S. § 39:3C-8