Exhaust baffles discourage exhaust from escaping a motorcycle engine. Partially damming the exhaust is not necessarily bad. As a result of a chain of physical events beginning at the carburettor, motorcycles run best when there is "back pressure." The tailpipe is the end of that chain of events and the engine makes the most horsepower when all the exhaust can not spill out at once. Baffles also make motorcycles quieter and so they come from the motorcycle plant tuned to please people who like to complain about motorcycle noise. Drilling a hole through them makes them a little louder and a little more likely to please people who like to ride motorcycles.
Unbolt the front and rear mufflers from the exhaust bracket with a hex socket and a socket wrench. Remove the heat shields from the front and rear mufflers with a flathead screwdriver.
Check the bottoms of both mufflers for Allen head screws. Unfasten any screws you find with an Allen wrench. Save the screws.
Gently tap each muffler with the side of your closed fist several times. Pull the mufflers off the exhaust pipes with your hands.
Remove end caps, if applicable, with your hands, an Allen wrench or a screwdriver, depending on your type of motorcycle.
Look inside both ends of each muffler for visible baffles to determine if the baffles are removable or welded into the muffler. Pull removable baffles out of the muffler shell before modification. Modify non-removable baffles in the muffler shell.
Chuck a 3/8-inch drill bit that is at least 12 inches long into an electric drill. Turn each baffle or each complete muffler on end with the exhaust side up and the header pipe side down.
Drill a 3/8-inch hole into the centre of each baffle.