It's a dirty job but somebody has to do it.
And that somebody should be you since repacking the exhaust on your dirt bike or ATV is a pretty simple and straightforward process.
First, know when to say when. It doesn't matter if you're riding a 2-stroke or 4-stroke engine, dirty exhaust packing is dirty exhaust packing. The sound is a dead giveaway. Instead of a throaty muscular tone, the exhaust emits a tin can pitch. You'll know it when you hear it. Additionally, if you're riding in events or areas restricting decibels, old exhaust packing sometimes makes the difference between coming in under the posted sound limits and sitting out.
You'll also experience some horsepower loss. So when one or both happen, it's time to repack the exhaust. But if you're the meticulous type, you won't let it get this far. Like a lot of other maintenance needs, check the owner's manual for hour intervals or quite often a few years of riding experience lets you know when it's time before the loss of power hits.
OK, now it's time to unpack.
Depending on the make and model of the exhaust you'll have to drill out the end cap rivets, using a rivet gun, and replace the drilled out rivets after positioning the new packing. When removing the rivets, use the correct drill bit so you don't damage the end cap and the holes for the rivets. Install the correct size rivets and don't use cheap replacements otherwise risk losing the end cap. If you're lucky, some cans have a bolt on the end which easily removes and reattaches. So keep this little tidbit in mind next time you go shopping for an exhaust upgrade!
This exhaust has rivets that need removing so the exhaust packing can be changed
Once removed, the exhaust, muffler, slip-on (all the same just depends on what circles you float in) needs cleaning. Use a contact cleaner or other type of solvent to rid the inside of carbon build-up. Now is a good time to shine the outside if you wish.
After the inside is clean and dry you can add the fresh packing. Most exhaust packing is made from fiberglass. It's similar to attic insulation so if you've ever worked with the stuff, it's pretty nasty. Wear gloves when handling the packing as it's prickly and itchy. It also might be a good idea to wear eye protection so it doesn't cause irritation. But, luckily, the exhaust packing is much more manageable then 1,000 square feet of insulation.
The exhaust packing likely comes in a sheet though some like Big Gun is pre-rolled and simply inserts inside any of the company's exhaust pipes. You want a tight fit otherwise you'll burn through it pretty quick so cut the packing to the muffler length, roll like a sleeping bag, and determine whether you can position inside the muffler without crumpling but maintaining a tight, secure fit. If not, you'll need to size accordingly. Using tape like electrical or masking tape to compress the roll allows for maximum amount of exhaust packing. The tape quickly burns off leaving you with a full pipe.
Once finished put the end cap back on using the rivet gun or reattach the bolt. Start the engine and you might initially see some excessive smoke, which is normal, and some packing might spit out, also normal. If you didn't place enough packing you'll know by the tin can sound otherwise enjoy the new horsepower and get out and ride!