There is always one person at the track with a bike that is ten times louder than anyone else’s, this person tends to be towards the back of the pack on race day and it’s a dead giveaway to how much time they are dedicating to bike prep. Repacking your muffler is a quick and easy process, and if you do it often enough, it isn’t even a messy job! Follow this how-to guide on muffler repacking to ensure your bike always passes emissions tests on race days and avoid being “that person” with a bike that sounds like you are banging an old fuel can with a cricket bat!
Why should you repack your muffler?
For starters, more and more tracks are being closed or restricted due to noise complaints, so turning up to your favorite place to ride with an excessively noisy machine will just inflame any issues. Secondly, dirty packing will restrict the flow of exhaust from your motor which as a result will rob your bike of power. If you have just spent money on a performance exhaust but fail to keep the muffler packing fresh, you may as well have not even bought the pipe in the first place!
How often should you repack your dirt bike muffler?
The Yoshimura factory suggests repacking a road muffler from 10,000 to 15,000km’s and off-road systems every 10-15 hours to maintain peak performance. Muffler packing will deteriorate particularly quickly on two-stroke machines as the addition to oil to the fuel being burnt produces more carbon which chokes a bike even quicker.
How to repack your dirt bike muffler:
Step 1: Remove the muffler from your bike (make sure if you have been riding the muffler has cooled down completely) and assess if the muffler has rivets only holding the muffler together or if one end is bolted together. If rivets only you will need to drill these out to get it apart, so make sure you or someone helping you know what they are doing when drilling out rivets, and bear in mind you will need to rivet the thing back together before you can ride so get prepared!
Step 2: For two-stroke mufflers, remove the screws at the end of the muffler closest to the motor. There should be no need to drill the rivets out at the tail end as the baffle and packing can be removed easily from the opposite end. This will save time drilling and re-riveting the end cap on.
For four-stroke machines, it is easier to remove the end cap of the muffler and perform the procedure from that end.
Step 3: To assist pulling the muffler apart use a box cutter knife to cut the silicone seal on the muffler, you may also need a rubber hammer to tap against the muffler bracket to assist getting it apart. Be careful not to damage the muffler with this, if you have to hit too hard you may have missed a rivet somewhere. Once the muffler is apart, remove the baffle and discard old muffler packing, you may want to wear gloves for this process as the packing can irritate your skin.
Step 4: Clean and inspect the baffle for damage as the baffle can crack or may be damaged from a crash and should be replaced or repaired to ensure the exhaust flow is not hindered in any way. To clean carbon from a muffler you can use a high strength degreaser or you may require a high-pressure bead blaster if the carbon is severely built up.
Step 5: Once everything is clean and dry you can add the fresh packing. With two-stroke machines, it is easier to wrap the baffle in the packing material firmly and use a small amount of masking tape to hold everything in place before reinserting it back into the outer chamber of the baffle.
For four-stroke machines, the most common method is to insert the baffle back into the outer chamber and add the packing material after that. Again you want the muffler to be packed firmly inside the entire muffler so use something to assist packing the material down all the way inside the chamber.
Step 6: Once the muffler is completely packed you are ready to put it back together. Just before you push the two pieces completely together use the box cutter to trim any excess packing away for a neat finish. Press the muffler together and make sure all of the bolt/ rivet holes are lining up and the muffler hasn’t been put together on the wrong angle.
Step 7: Replace the screws/rivets and reseal the muffler with heat resistant silicone sealant. Clean any excess off with a rag and check the pipe to ensure everything is tight and in the right place.
Step 8: Put the muffler back onto your machine, ensure all parts of your bike are tightened to the correct torque settings and you are ready to moto!
This article is originally posted at MXStore.
