Dirt Bike Exhaust Packing 101

Dirt Bike Exhaust Packing 101

It’s easy to forget about.  It’s also easy to just plain ignore it, but you will be reminded by the effects of blown out exhaust packing every time you ride your dirt bike.  Your bike will not only be louder (not in a good way), but you will also lose low end torque and overall horsepower from blown out exhaust packing.  Yes it can be a little inconvenient to take your muffler or silencer can off of your bike, but once you get the whole process down, it can be done in no time.  You’ll notice a quieter ride and more importantly, you’ll notice that the power of your dirt bike is where it should be.

Moose Competition Muffler Packing

One of the biggest questions is how often the exhaust packing should be replaced.  The answer: when it needs to be.  How long the packing lasts depends on the rider, the bike and the quality of the packing.  A good rule of thumb for the average rider, though, is about every 20 hours of riding.  If you only ride your bike casually, you might be able to go all year or even longer.  If you ride extremely hard in some rough terrain, you can blow out your packing in just one day!  A good sign that you need to change it is if you start to see some discoloration on the can or muffler.  You will also notice your bike get louder and it will not be as snappy as it once was.

Water will also speed up the deterioration of the exhaust packing.  When you wash your bike, make sure that you always put the bung plug in the end cap to prevent any water from getting inside the muffler.  Also, running your bike too lean can break down the packing prematurely too due to increased exhaust temperatures, so it’s a good idea to make sure your bike’s air/fuel ratio is where it needs to be.

So what exactly is the packing and what does it do?  Inside your dirt bike muffler or silencer is the exhaust core, which is a tube with holes in it and is often covered in steel wool on newer pipes.  Between the core and the outside can sits the exhaust packing.  The packing itself is a mat or pillow that is usually some kind of fiberglass (or similar material).  Think home insulation, but far more durable and packed tighter.  (Note: Never use home insulation as packing.  It will not hold up to the heat and airflow of the exhaust).  The purpose of exhaust packing is to absorb as much of the sound waves coming from the combustion of the engine as possible.  The softness allows the sound waves to dissipate between the fibers of the packing.  Once it wears out, the packing cannot trap as many sound waves, plus the exhaust no longer has a straight shot through the muffler and gets diverted in between the core and can, which results in power loss.

Now that we have the basics down, here is a general guideline for replacing your blown out dirt bike exhaust packing.

  1. Remove the muffler from the bike.  This makes working on it easier.  Some bikes, you might have to remove the whole exhaust system.
  2. Now you will need to remove the end cap of the muffler.  Different brands and styles have their own ways of holding the cap to the muffler.  Some have rivets, while others are held on by brackets.  With the rivets or brackets removed, you can now use a rubber mallet to tap on the sides of the cap to loosen it.  You can also hold on to the cap while gently tapping the mounting bracket on the can until the cap is loosened.  With it loose, you can pull the cap off.
  3. At this point you will want to put on a pair of work gloves and even long sleeves and a mask because you will be working with loose fiberglass.
  4. Pull out the exhaust core tube with the blown out packing.
  5. With the core out, you can now remove all of the old packing and discard it.  If there is steel wool around the core, you can take a wire brush to it, ensuring that there are no fibers left on the core.
  6. Now take the core and place in on the edge of your new packing material.  If it is not a direct fitment, you will want to cut the sheet so it is about an inch and a half longer than the core.  This will allow it to compress and still have full coverage when you reinstall it.  To make this step easier, there are direct fitment packing cartridges that slip right over the core with no cutting necessary.
  7. It’s now time to reinstall the core into the can with the new packing.  If you are not using the cartridge style, you can use a little bit of masking tape to hold the packing secure, which makes it easier to fit the core and packing back into the can.  Once it encounters heat from the exhaust, the masking tape will lose its strength and allow the packing to fill the can and eventually burn off completely.
  8. Before you place the end cap back on, you will want to spread some high-temperature silicone or RVT sealant around the base of the cap.  This will ensure a tight seal and prevent water from seeping into the can.
  9. With the cap back in place, you can now attach it with rivets or brackets.
  10. Reinstall the muffler or exhaust system on to the bike
  11. Let the silicone cure for as long as the packages says before starting and running your bike.
  12. When you do start the bike, it may spark or smoke for a bit.  You will want to make sure that there is nothing flammable behind the bike.  Once the sparks and smoke stops, you are ready to ride.

There you go, it’s that easy.  Once you get the process down, you can fly through it so you never have to suffer unnecessary power loss and annoying decibels from blown out packing again.

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