150cc stock exhaust drilling/mod with pictures

[moisesanguiano]

Hey all, so ive been looking around online regarding taking apart the muffler and drilling/gutting the inside. I figured out the general process of taking off the muffler and cutting it open, but i couldnt decide on where exactly to cut it, and what the inside looks like. I heard there were baffles inside, and S shapes pipes and whatnot. So I decided to go at it and cut it open. I was pretty surprised on how it's designed, really restricted. The muffler is still apart as i'm not sure exactly what I want to do yet, so i've taken pictures and wanted to write about my findings for those who are fairly new to scooters (like me) :

(Numbers in black)

Pic#1:I had to drill out the rivets in order to slide off the aluminum outer tube and rear cap. The front one is welded to the muffler body and inner pipe so that stays there. Mine was super rusted between the outer tube and body so it was a struggle to get it off. I then cut it around the middle (not straight through though)

#2: That pipe sticking out was actually welded to the other half of the muffler so i wiggled both halves back and forth until it broke loose.

#3: A view of the inlet and muffler tip, for reference. As you can see, I originally drilled the back plate like others have done, but i just said screw it and decided to cut the darn thing.

#4: Inside view of both halves. On the right half, you can see where the pipe sticking out of the left half used to be through that wall.

#5: Close up of the left half. This pipe is where the exhaust initially enters the muffler. As you can see it bends 180° to face the opposite direction.

Continues to next post

[moisesanguiano]

#6 : Close up of right half. Here you can see through the first wall and to the second wall. It looks like there's a total of 2 walls, 3 chambers. The first chamber is from the end of the left half (pic #5) to the first wall, the second chamber from the first wall to the second, and the third chamber is behind the second wall(the holes drilled in the back plate lead to this chamber). Weird thing is, the exhaust doesnt exit through the tip from the third chamber, it's from the second. I'll show the exhaust path next.

#8: So here's how the muffler...muffles. The exhaust comes in through the left half, up the curved pipe, through the 180° bend and into the first chamber. Then it flows through pipe #1 (in red) into the furthest (3rd) chamber, where it comes into the second chamber via opening #2 (red). Finally, it flows into pipe #3 (red) which leads to the tip and out the muffler.

I hope this sheds some light on what the inside of these mufflers consist of. I know it would've helped me, so now I hope this can help others. Now I have some questions. So now that I've got the thing open, what would you experienced members recommend? I don't think I want to completely gut it out due to it being too loud, but i definitely wanna take some stuff out cause its ridiculous in there lol. I was thinking about removing the first wall (pic #9) and maybe also cutting the bended pipe (#10). Since the tip pipe comes from the second chamber (which would be one big chamber after removing the first wall), the third chamber will be useless. That being said, should i leave the drilled holes in the back open, plug them, or plug up both the holes and the third chamber? It doesn't really make sense to plug the holes and not the chamber, just to have exhaust sit back in there. Any input is appreciated. Thanks !

[TN rider]

What did you end up doing? Performance?

[Shadowfire]

Without an oversized top end, its just making the bike louder, with no noticeable improvement in performance.

[gino pi]

i did mine, it came out good. i cut off the backfire screen area on the tube. i then cut down the total length of the first chamber, and welded it back together with no fiberglass packing inside. so its just a double chamber exhaust now. its lighter by alot and its still quiet. its good i think, and i think i need a larger jet now.