California Customers Search Products | MIC Statement on Emissions | FAQ

This document contains the Motorcycle Industry Council's interpretation of California law and regulations related to aftermarket exhaust systems. MIC has prepared this document in an effort to clarify related issues for dealers in California. Please contact memberservices@mic.org with any questions.

Frequently Asked Questions about Aftermarket Exhaust Systems
for Motorcycles and ATVs in California

What exhaust systems and slip-on mufflers can a California dealer sell or install without violating California air pollution control requirements?

Aftermarket exhaust systems that can legally be sold under California's air pollution control requirements are (1) systems that are designated "replacement parts," (2) systems considered "modified parts" for which an Executive Order has been issued, and (3) systems only for use on "racing vehicles" that have been adequately identified as such.

What exhaust systems and slip-on mufflers are considered "replacement parts"?

Under California Air Resources Board (CARB) regulations, "Replacement parts" are parts that have the same effect on emissions as the original equipment part that they are intended to replace. In the case of exhaust systems for motorcycles and ATVs, CARB considers aftermarket exhaust systems to be replacement parts if either of the following conditions is met:

1. The vehicle was not originally equipped with a catalyst and all emission controls originally connected to the exhaust system are reconnected to the aftermarket exhaust system and are functioning properly. (It is rare for other emission controls to be connected to a non-catalyst motorcycle or ATV exhaust system, but examples include an exhaust gas oxygen sensor or an air injection system.)

1. The vehicle was originally equipped with one or more catalysts, but the catalyst(s) are retained and all emission controls originally connected to the exhaust system (e.g., an oxygen sensor) are reconnected to the aftermarket exhaust system and are functioning properly.

As long as they meet the above definition of "replacement parts," "slip-on" mufflers are legal for use in California unless the muffler being replaced contained a catalyst.