California regulates motorcycle aftermarket parts that have the potential to impact emissions. Under California Vehicle Code section 27156(c), the law states that
No person shall install, sell, offer for sale, or advertise any device, apparatus, or mechanism intended for use with, or as a part of, a required motor vehicle pollution control device or system that alters or modifies the original design or performance of the motor vehicle pollution control device or system.
In most cases, the sale and use of emissions related aftermarket parts on motorcycles is prohibited unless it is either a "Replacement Part" or is a “Add-on or Modified Part” that has received an exemption by the Executive Officer of the Air Resources Board (ARB), such as an Executive Order.
Under Title 13 of the California Code of Regulations section 1900, Replacement Parts are defined as:
Any aftermarket part intended to replace an original equipment emissions-related part and which is functionally identical to the original equipment part in all respects which in any way affect emissions (including durability).
Examples of potential Replacement Parts may be where an aftermarket exhaust system is fitted to a motorcycle that was originally certified without a catalytic converter, or an aftermarket exhaust muffler that is fitted to a motorcycle downstream of a catalytic converter.
Add-on and Modified Parts
Under Title 13 of the California Code of Regulations section 1900, Modified Parts are defined as:
Any aftermarket part intended to replace an original equipment emission-related part and which is not functionally identical to the original equipment part in all respects which in any way affect emissions.
Under the same section, Add-on Parts are further defined as:
Any aftermarket part which is not a modified part or a replacement part.
An Add-on or Modified part requires an ARB engineering evaluation in order to be exempt from the prohibitions under California law. If the part or modification is shown to not increase vehicle emissions, it is granted an exemption to emission control system anti-tampering laws. This exemption is called an Executive Order (EO) and allows the modification to be installed on specific emission controlled vehicles.
Add-on or Modified Parts that have not received an exemption may only be used on a motor vehicle that is used exclusively for closed-course competition. In addition, retail sellers of such parts should be aware that under Title 13 of the California Code of Regulations section 2222(f), it states:
Each person engaged in the business of retail sale or installation of an add-on or modified part which has not been exempted from Vehicle Code section 27156 shall maintain records of such activity which indicate date of sale, purchaser name and address, vehicle model and work performed if applicable. Such records shall be open for reasonable inspection by the Executive Officer or his/her representative. All such records shall be maintained for four years from the date of sale or installation.