Modding A Stock Muffler

If your stock muffler is looking nasty, getting clogged, not loud enough for you, or you want to try and get a little bit of a free performance gain, you may not need to buy an expensive aftermarket exhaust. Obviously a 2 stroke will get much better performance if you do go out and buy a nice expansion chamber pipe, but that's not always in the budget. This style of muffer is on a lot of 2 and 4 stroke scooters from 49cc up, so it may be a practical mod for you.

I started out by drilling out the rivets on both ends.

With all the rivets completely drilled out I could begin to pull the muffler from it's case. This one wasn't bad and only required a bit of twisting and shaking (sounds like a bad dance) to remove. Sometimes they are more stubborn and will need a bit of persuasion with a mallet and possibly some WD-40.

It should separate into 3 parts. The muffler itself, the outer sleeve, and a chrome end cap.

I used a sawzall to cut the muffler down the middle.

The inlet side basically just has a cone and the outlet side has a chambered type of setup.

I don't really want it much louder, but I wanted to be sure nothing was restricted. I drilled 6 1/2" holes as shown. I used a flashlight and looked in anywhere I could to be sure nothing is restricted or clogged.

I've completely disected other mufflers before and messed with them to get different volume levels. If you want it extremely loud you can completely gut the muffler. Cut off everything from the actual muffler to just leave the inlet side's end cap and use the chrome outlet endcap. You can experiment by not cutting out much or doing much drilling at once. It's up to you and just how loud you want it.

I was satisfied with the small change I made, so I welded the two halves back together.

I then put the muffler back into the casing (which I painted with flat black BBQ paint). I brushed out the rust and polished the end cap and installed it as well. Then I hoined them all together with sheet metal screws. You could choose to rivet everything together instead. The screws are a bit easier to remove and replace if you decide to modify it later or want to check anything.

Nothing spectacular, but it sure looks better than the rusty old part I started with. I should note that you can not only experiment with different setups inside the muffler as I mentioned earlier, but you can also shorten the muffler to make it look better or sound different if you so desire. Be creative with it.