The US Federal Standard is 80db for motorcycle manufactures only and testing is done much different than what each state or city is doing. Each state and city is developing their own standards based on the new stationary on-highway motorcycle sound test standard released by SAE. (SAE J2825).
Information from the AMA:
The SAE J2825 on-highway motorcycle sound test procedure is similar to the one used for the SAE J1287 off-highway motorcycle test. The street bike measurement requires holding a calibrated sound meter at a 45-degree angle 20 inches from the exhaust pipe of a running engine. The procedure spells out how to do the test with the bike at idle, at a predetermined engine speed ("Set RPM Test"), or by slowly increasing the engine speed of the bike, known as the "Swept RPM Test."
The SAE J2825 standard, prepared by the SAE Motorcycle Technical Steering Committee, recommends a decibel limit of 92 dBA at idle for all machines or -- using the Set RPM or Swept RPM Test -- 100 dBA for three- or four-cylinder machines, and 96 dBA for bikes with fewer than three or more than four cylinders.
If you get pulled over for sound, make sure the officer is qualified to do the testing and has the calibrated equipment to do the test. If the officer is making a judgment call using his ears, fight it!
Last edited by fugginfabrication; 02-24-2010 at 06:45 PM.