Motorcycle racing in Bucks County is subject to certain restrictions when it comes to the type of exhaust systems that can be used. The motorcycle must be equipped with a silencer or other effective noise suppression system, in good working order and in constant operation. Federal law prohibits any modification to this exhaust system that would cause the motorcycle to exceed the federal noise standard. The use of the motorcycle with a modified exhaust system of this type is also prohibited.
OEM exhaust systems are inherently more restrictive than aftermarket racing exhaust systems. The reason for this is due to all kinds of government regulations, which limit the amount of air that can be breathed out by an engine. This means that, just like us human beings, a motorcycle engine can only inhale the same amount of air that it can exhale. If you can increase the amount of air breathed out, then you can also increase the amount of air breathed in, resulting in greater performance and more power. Motorcycle exhausts come in many varieties depending on the type of engine and its intended use. A two-cylinder bike can have separate exhaust sections, as seen on the Kawasaki EX250 (also known as Ninja 250) in the US or GPX 250), or a single exhaust section known as two-in-one (2-1).
A complete system can be purchased as an aftermarket accessory, also called 4-2-1 or 4-1, depending on your design. In the past, these bikes came standard with a single exhaust silencer, a practice that lasted until the early 2000s, when EU regulations on noise and pollution mostly suspended this practice, forcing companies to use other methods to increase motorcycle performance. In addition to these restrictions, there are also certain exemptions for racing motorcycles. According to § 205.169 of the Federal Register, exhaust systems designed and marketed solely for use on racing motorcycles are exempt from certain provisions of this subpart. Furthermore, a test motorcycle used for selective compliance auditing testing of exhaust systems must be an object-class motorcycle that has been assembled using the manufacturer's normal production process, in stock configuration, including the exhaust system, and sold or offered for sale commercially. The manufacturer of the exhaust system must perform a valid test in accordance with the appropriate test procedure specified in Appendix I for each exhaust system selected for testing under this subpart.
Use on motorcycles subject to EPA noise regulations constitutes manipulation and constitutes a violation of federal law, unless it is proven that such use does not cause the motorcycle to exceed applicable federal standards. Original equipment exhaust systems that are also sold as replacement systems for the same motorcycle configuration do not need to be tested under this subpart if they have been tested or represented in a test report under subpart D of this part. Category means a group of exhaust systems that are identical in all material respects with respect to the parameters listed in § 205.168 of this subpart. If the manufacturer produces 50 or more of the specified category, upon receipt of the test request, the manufacturer shall select and test a sample of exhaust systems for the category specified in the test request in accordance with this subpart and the conditions specified in the test request. In a two-stroke engine, such as the one used on dirt bikes, a protrusion in the exhaust pipe, known as an expansion chamber, uses exhaust pressure to create a pump that squeezes more air and fuel into the cylinder during the intake stroke. Exhaust system components that are sold as separate products that are incompatible with the original equipment components necessary to manufacture a complete exhaust system, or that do not meet the standards prescribed in this subpart in such configuration, may be tested with non-original equipment components, provided that the provisions of § 205.169 (e) (ii) (B) are met. In production road racing motorcycles, like all motorcycles competing in the MotoAmerica Series, optimal performance is always sought after and function is more important than form. Demonstration that the specified exhaust system category has passed a new test conducted in accordance with § 205.171 and the conditions specified in the test request is required. The Administrator may complete these tests earlier than required on request from manufacturers accompanied by voluntary cessation of commercial distribution of exhaust systems of said category manufactured at their plant being tested. To be accepted as an alternative test procedure it must be able to identify all test exhaust systems that would not meet noise emission standards prescribed in § 205.166 when tested according to measurement methodology specified in Appendix I.
Use on motorcycles subject to EPA noise regulations constitutes manipulation and constitutes violation of federal law unless it is proven such use does not cause motorcycle to exceed applicable federal standards.