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Motorcycle Exhaust 201 : Noise, C.A.R.B and more


Open most exhaust catalogs or moto exhaust suppliers' websites and you're likely to see a pile of disclaimers that makes you feel as though Johnnie Cochran bought a few shares of their stock.

That's because, ultimately, the web of laws is simply too dense and complex for a retailer or manufacturer to recommend a product to every single biker and be sure that that motorcyclist will not be in violation of any federal, state, or local laws.

The purpose of this document (for you) is to figure out what all the mumbo-jumbo means. The purpose of this document (for us) is to let you know why the mumbo-jumbo matters. Mumbo-jumbo. Man, that is fun to say. Do it out loud a few times. Doesn’t that feel funny with your lips all over the place?

Back to business: We’re going to touch on noise violations very briefly in regards to street-going machines, and then tuck into C.A.R.B. and federal emissions requirements. (For street vehicles. Competition and off-road bikes have vastly different rules.)

Don't forget to read Motorcycle Exhausts 101!

Ultimately, the onus of responsibility to be legal is on you, in the equipment you bolt to your bike, the way you ride it, and where you ride. We want to educate you so you can evaluate your riding area and style, and make an appropriate equipment choice that minimizes your friction with the folks who enforce the law of the land.

The law

OK, so let’s dig into motorcycle emissions. Motorcycle laws tend to govern two areas of your waste products: sound and pollution. We’re not lawyers here at RevZilla, so this document is not meant to be a legal defense when you get pulled over at a PETA gathering in Cali for scorching roadkill with that cool flamethrower kit you put on your LAF pipes. Instead, we are trying to make you aware of the laws that exist, and help you make informed decisions. With all that said, do the right thing. Seriously. It’s rare that folks get burnt very badly in a legal sense when they are trying to stay within the boundaries of the law. If you don’t want The Man on your case, don’t give him excuses to pull you over. In the same vein, if you are hellbent on running open drags and the biggest jets you can buy, be aware that it is possible you will be ticketed multiple times.

There is a dichotomy, often, between the laws on the books and laws being enforced. Often, talking to people in your locality or state who know the laws is a good start at figuring out what is permitted in your area. Your state motor vehicles agency, an inspection station, the local motorcycle shop, or a local lawyer who specializes in motorcyclists can be helpful here. Expect (and volunteer) to pay them for their time counseling you. Answering questions usually is not an efficient or profitable use of the part of their day that they could use to do something else. A box of doughnuts goes a long way here at your local motorcycle shop.


As far as sound is concerned, local, state, and federal laws are all over the map. The patchwork of statutes is staggering. The laws are often written by folks who are not motorcyclists, scientists, or acoustic engineers. Rather, they are written by bureaucrats, amended by other bureaucrats, and made into laws by some other folks who ultimately do not spend their weekend jammin’ gears on a Shovelhead. The sound tests are frequently not described well, and many are not even repeatable. If you’re like most bikers, you occasionally venture into different states or municipalities, so what might have been legal at home is no longer legal in, say, Illinois. The federal government used to (sort of) govern noise requirements, and then they charged the states with setting and enforcing their own rules; hence the lack of clarity. Here are some general rules to live by:

  • Running without mufflers is living on the ragged edge of getting a ticket in many places
  • Running an obnoxiously loud aftermarket exhaust with a muffler is living on the ragged edge of getting a ticket, too
  • Many noise-related tickets can be avoided by good judgment and a right wrist that takes it easy at the right times with the barkiest pipes
  • Most muffled aftermarket systems with a dB killer in place will not arouse the attention of local law enforcement
  • Use your noodle — if it sounds crazy-loud after you install it, it probably is
  • Break the laws if you must, but know the consequences — typically a hefty fine and a re-inspection are in your future if Johnny Law pops you for your bike singing its work song a little too loud


Much like the noise laws, these are a mess. There are some federal emissions standards you can read here. Go ahead, we’ll wait. Mind-numbing, no? In practice, these laws have to do with vehicles being certified to be sold here. Once they’re here and on the roads, the Feds (to the best of our knowledge) are not out on the road checking charcoal canisters. They leave that up to the states. In essence, getting your hands on a vehicle with a legitimate VIN in stock form that did not meet federal specs would be pretty difficult.

Each state has its own emissions and inspection requirements. Much like the section about the law, talk to the people who know the laws and the ones who enforce them. It’s up to you to make sure your bike’s legal.

Now, for you Californians: You have a whole separate entity governing your life, called the California Air Resources Board (CARB, for short. Oh, the irony.)

They have a super-helpful Motorcycle FAQ regarding aftermarket parts. To restate what we said earlier, none of us here at the Zilla rock a JD, but this stuff is in reasonably plain English.

Effectively, CARB says that they only care what you are doing to your emissions system. Specifically, they include the following list of parts in their definition of items affecting “emissions”:

  • Catalytic converters
  • Cams
  • Fuel controllers
  • Carburetor jets
  • Sprockets

They also state that “direct replacements to stock parts” are not affected either. They give specific examples of:

  • Spark plugs
  • Plug wires
  • Air cleaner elements
  • Headers and mufflers for non-catalytic converter-equipped bikes that do not render any OEM emissions control devices inoperable

CARB does make mention of the fact that manufacturers must “maintain records with specification data that confirms their replacement parts are indeed functionally identical” to the OEM parts. They also provide for a manufacturer to have a part exempted from the law. In order to get that exemption, the supplier must do two things:

  • Make certain the part does not reduce the effectiveness of any required emission control device on a motorcycle
  • Demonstrate that applicable emission standards are being met with the part installed on the bike

How do we interpret this? Heck, we ask our lawyers! And we stay out of Cali! In all seriousness, there are a few things to consider. First is CARB’s newly aggressive policy of enforcing these California motorcycle laws. Several large manufacturers and distributors of exhausts in California have paid or are fighting huge fines, or have otherwise reached a settlement with CARB. We’re not going to name names, but suffice it to say that if you live in a household with motorcycles, these suppliers are household names to you.

Next, consider that the process for obtaining an exemption is typically considered costly and difficult by most manufacturers, hence the very short list of parts with an exemption.

It looks like any type of a “cat-back” (read: slip-on) exhaust that does not remove a catalytic converter, PAIR valve, or any other air-injection devices should not be problematic. We don’t hail from the great state of California, but if those laws are interpreted in plain English, that’s how they appear to read. Given the short list of exempted catalytic exhausts, unless you have a carbureted bike, you’re probably going to want to avoid most full-system exhausts if you want to stay legal.

Insofar as fuel controllers, really, only the manufacturer and CARB know if something is performing within legal parameters. We spoke with a representative of CARB at the time of this writing, and he was unaware of a list of approved fuel controllers. The same representative told us that CARB will chase manufacturers as well as work with the CHP to find end users who are breaking the law. In the same conversation, he told us that California has no motorcycle safety or emissions inspections.

A word of note: See “sprockets” on the emissions parts list? That’s because they test these things at a certain speed. If you have dropped a few teeth on your front or jumped up a few on your rear, that acceleration came at the expense of higher rpm at a given speed. Thus, your engine spins faster and emits more junk into the air. California considers sprocket changes a potential CARB violation.

Final thoughts

The CARB is trying to keep the air clean. Your neighbors do not want to hear your LAF pipes at two in the morning when you roll in from that run to Arkansas. There are a myriad of currently unclear laws. Obeying them seems to be largely on the honor system for bikers at this time.

Do the right thing.

We respect the fact that as an adult, you are capable of making good decisions. There’s plenty of hot-rodding and noise-making you can do at reasonable levels and stay within the boundaries of what is legal. If you do want to “ride dirty,” know the potential consequences of your actions — fines and other related punishments.

Ultimately, like many other things in motorcycling, the burden of responsibility falls upon the rider. Learn. Educate yourself. Make good decisions, and take responsibility for the choices you have made as your own actions. If you need any help, we’ll be here.

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