Lawn mower engines are often fairly loud as they only have a small muffler on them and they are not contained as car engines are, but the small muffler should at least keep the engine sound to a bearable level. Over time, the muffler can become cracked or the muffler gasket will deteriorate and the muffler will be become useless at muffling the air blowing out of the engines exhaust port.
Things You'll Need
Allow the lawn mower engine to cool down for several hours before handling the muffler as it will be extremely hot right after you shut off the engine.
Locate the muffler bolted onto the front or side of the engine block. Mufflers are usually bolted on the exhaust port on the engine block with two or three bolts.
Fit the proper size wrench on the muffler bolts and unscrew them.
Inspect the muffler for any cracks. Over time, water will rust and crack the muffler. Purchase a new one if the old one is very rusty and cracked because a new mower engine muffler only costs $10 to $20, as of 2010.
Peel the muffler gasket off the side of the engine block and replace it with the new one.
Tighten the muffler over the gasket onto the side of the engine block.