The way a dirt bike's muffler works

The way a dirt bike's muffler works

The way a dirt bike's muffler works is very simple, and so is repacking it. In a nutshell, your muffler is a large tube, with a narrower, perforated tube inside it. Between the two tubes is “soft stuff”, generally fiberglass.

When fuel explodes in your piston, the sound and pressure wave travels down the exhaust to the muffler. The soft material absorbs a lot of the sound waves – it's the same science that allows movie gunmen to fire through a convenient pillow to muffle their shots.