Have you ever wondered what laws govern the removal of emissions????
Below is a dealer’s guide from a bike manufacturer.

EMISSION CONTROL INFORMATION (United States only)
The Clean Air Act, which in the Federal law covering motor vehicle pollution, contains what is commonly referred to as the Acts “tampering provisions:”
“Section 203 (a) The following acts and the causing thereof are prohibited-
(3) (A) for any parson to remove or render inoperative any device or element of design installed on or in a motor vehicle or motor vehicle engine in compliance with regulations under this title prior to its sale and delivery to the ultimate purchaser, or for any manufacturer or dealer knowingly to remove or render inoperative any such device or element of design after such sale and delivery to the ultimate purchaser.
(3) (El) for any person engaged in the business of repairing, servicing, selling, leasing, or trading motor vehicles or motor vehicle engines, or who operates a fleet of motor vehicles knowingly to remove or render inoperative any device or element of design installed on or in a motor vehicle or motor vehicle motor engine in compliance with regulations under this title following its sale and delivery to the ultimate purchaser. . .”
Note: The phrase “remove or render in operative any device or element of design” has been generally interpreted by the government as follows:
1. It does not include the temporar,, removal or rending inoperative of devices or elements of design in order to perform maintenance. 2. It does include: a. Adjustment of vehicle components such that the emission standards are exceeded. N. Use of replacement parts which adversely affect the performance or durability of the motorcycle. c. Addition of components or accessories that result in the vehicle exceeding the standards. d. Permanently removing, disconnecting, or rendering inoperative any component or element of design of the emission control systems.
Regarding these dealer responsibilities as they to this parts catalog, you will notice that certain items are identified as “OFF-ROAD USE ONLY or “RACING USE ONLY.” These items do not comply with emissions regulations issued by the United States Environmental Protection Agency and should no be used on any motorcycle which is intended to be used on the public roads.
Also, use only those items which are applicable to the motorcycle in question. Examples: 1. Do not install oversize rear sprockets identified as “OFF-ROAD USE ONLY” in this parts catalog on dual purpose models which are intended to be used on public roads. 2. Carburetor components {jets, throttle valves, etc.) should be used on the applicable models) noted in this parts catalog. WE RECOMMEND THAT ALL DEALERS OBSERVE THESE PROVISIONS OF FEDERAL LAW, THE VIOLATION OF WHICH IS PUNISHABLE BY CIVIL PENALTIES NOT EXCEEDING $10,000 PER VIOLATION.
TAMPERING VVITH NOISE CONTROL SYSTEM PROHIBITED:
Federal lox prohibits the following acts or the causing thereof: (1) The removal or rendering inoperative by any person other than for purposes of maintenance, repair, replacement, of any device or element of design incorporated into any new vehicle for the purpose of noise control prior to its sale delivery to the ultimate purchaser or while it is in use, or (2) the use of the vehicle after such device or element of design has been removed or rendered inoperative by any person.
Among those acts presumed to constitute tempering are the acts listed below: * Replacement of the original exhaust system or muffler with a component not in compliance with federal regulations. * Removal of the rnuffler(s) or any internal portion of the muffler(s). Removal of the air box of air box cover. Modifications to the muffler(s) or air intake system by cutting, drilling, or other means if such modifications result in increased noise levels.