From Hindle Exhaust:
Have you just purchased a brand-new Hindle muffler for your dirt bike? A General Muffler Warm Up Procedure should be done for ALL types of Hindle mufflers. Once the muffler is installed, give the muffler a chance to set the internal packing by leaving the bike at idol for approximately 15 minutes. Then, turn off the bike and let it cool down for approximately 15 minutes.