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Discussion Starter #1 (Edited)
Hi guys, this is only my second post on here but I always seem to just jump right in!

Just a little background, I've been a GM dealership Master Tech/Foreman/Driveability and Electronics expert for 34 years. I've been heavily involved with building/tuning/modifying everything from RV's to Indy cars for almost 5 decades. (Yikes, how did that happen? haha.) I've tuned all kinds of engines including Pirelli World Challenge GTS cars, Vintage Trans Am cars, high hp street cars, boats, supercharged PWC's, motorhomes, dirtbikes and now street bikes. Making vehicles work better hasn't been a hobby for me, it's been my entire life.

Anyway, one of my favorite things to do is making engines SOUND good. I don't think I've ever owned a vehicle of any kind that I didn't modify the exhaust on! My modified engine leaf blower even has a YZ85 muffler on it! My family is used to it, my wife still laughs about me cutting into the stock mufflers on her BRAND NEW 2012 Cadillac CTS-V Wagon THE DAY WE DROVE IT HOME! lol.

So recently my son and I bought brand new MT-09's. I instantly ordered the Akrapovic carbon system for my bike, obviously dropping ~10lbs or so was a big factor in that decision. But my son wanted to wait until his finances recovered from the bike purchase to order his Akrapovic system, even though the sewing machine sound of the bike was REALLY bugging him. haha.

So I looked at some of the pictures of the inside of these stock mufflers that you guys have posted online. (THANKS btw!) I didn't really want to do extensive cutting and welding on a muffler that we knew was going to be replaced by an aftermarket system soon. So I figured out how to make the stock muffler sound WAAAAAAYYYYYY BETTER without even taking it off the bike! (Geez, finally he gets to the point of this whole thread.) So here's how you do it...

Grab a flashlight and look in the muffler outlet. If you also look at the edge of the outside of the muffler can, you can get an idea of where the outlet pipe passes through the can. What you want to do is drill a hole in the outlet pipe ON THE INSIDE THE CAN PART of the pipe. Picture 1 shows me sliding a punch into the end of the outlet pipe. If you have a punch with a sharp end on it, you can put it in like I'm showing and hit the punch with a hammer to make a pilot indentation for drilling. Now get a long drill bit or a bit on an extension and drill a hole through the outlet pipe. There is another layer of the internal baffling/wall behind that outlet pipe, you can also drill through that one too. These mufflers are stainless so they're pretty hard to drill, you'll need good bits, a lot of pressure and drill slow.

Once you get a hole drilled, you can step up with bigger bits or if you have a die grinder and porting burrs, you can use them to enlarge the hole. The hole I made in the outlet pipe was basically the whole side of the pipe, approx 1" in diameter, maybe a little more. I used a porting burr to shape the hole cleanly but it doesn't have to be pretty, it just has to be as large as possible and without any edges that could make "flute like" noises.

The hole I made in the second wall further in was approx 3/4". You can't really go obnoxious loud by doing this so don't be afraid to make the holes big. The end result on my son's bike was NO WHERE NEAR as loud as my Akrapovic carbon with the insert in. But it sounds GOOD!!! Really good. I did before and after vids in my shop, but as usual it doesn't really convey the change that well. If we get a chance I'll try to do a drive-by with his modified stock exhaust bike and my Akro carbon bike for a comparison.

This mod is free, but it's assuming you have at least a drill and some long bits or a bit extension. It's obviously FAR easier than the mods where guys cut the can open and remove/re-route the internals. And it can be done on the bike, which is pretty cool. The end result also looks perfectly stock, nobody would ever know unless they looked in the end with a flashlight and actually knew what it was supposed to look like in there. Since it retains the stock cat, the sound isn't harsh or brash, it's just a little deeper and you can actually hear exhaust noise over the clutch/gear noise! It sounds like it should have sounded stock. And it's FREE!

Have fun guys and let me know if anyone tries it!

John

(I'll put the pics and links to the youtube before and after vids in a second post here.)
 

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Discussion Starter #2
In the last two pictures here you can't actually even see any of the outlet pipe, it's all open. The last picture shows the hole in the SECOND layer/wall pretty clearly.

Here are the links to the before and after YouTube videos...

Before Mod Video

After Mod Video


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Discussion Starter #3
(Thanks mods)

I went ahead and did a little more opening up on that inner wall. It's hard to tell in the picture but it's probably 1-1.5" wide now. That grey part you see to the right of the hole is the cat converter. If you really wanted to go crazy opening it up, you could basically have it come straight out of the cat and into the outlet pipe. It's still not harsh or loud, it sounds amazing actually. Again, all of this can be done ON THE BIKE.

Here's a picture of that inner wall cut out more and a video of what it sounds like...

Link to further modded muffler...


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Discussion Starter #5
I found one of the pictures another forum member posted, hopefully they won't mind me stealing it to use here! The red lines are where you're going in with the bit or porting burr. The blue circles are roughly where the holes will be. As you can see, you can make it pretty much wide open from the exit of the cat to the outlet of the muffler itself.

Hope this helps!...

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Discussion Starter #7
Yes thats the easy way to make more sound. But it wont make more power as the restriction is still there.
I never said it would make more power.

If you want more power and less weight, obviously you'd buy a complete aftermarket system. That will cost you roughly 10% of what the entire bike costs new. Not everyone wants to spend an additional 10% on their bike, and that's not including having it tuned for the aftermarket exhaust. And not everyone likes the looks of aftermarket parts and would rather keep their bike looking stock. But many of those owners WOULD like their bikes to sound less like a sewing machine and more like the 850 triple it is. This mod is for THOSE people.
 

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Discussion Starter #8
Well? Has anyone tried this mod yet?

My son said there was a really big difference in what I did the first round to when I opened up the inside wall larger the second time. HE LOVES IT! It's still not excessively loud or harsh, it just has a nice, clean sound to it.

He was 100% planning on ordering the Akrapovic carbon system like I have on my MT09 before I did this mod. He now really, really likes the sound of the exhaust so now it's a matter of spending $800 just to drop some weight. (And gain some power of course.) He said for now he has NO intention of spending that $800 to replace what the stock system sounds like after my mods.
 

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He was 100% planning on ordering the Akrapovic carbon system like I have on my MT09 before I did this mod. He now really, really likes the sound of the exhaust so now it's a matter of spending $800 just to drop some weight. (And gain some power of course.) He said for now he has NO intention of spending that $800 to replace what the stock system sounds like after my mods.
Very smart son you have (y) Use the money saved for a rear shock, money WELL spent.
 

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use the money saved for some rider coaching - money even better spent!
 

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I'm going to as soon as I find a way of doing the grinding.
 

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Discussion Starter #12
Thanks for the likes guys! And yes, my son is amazingly smart and a good person too! haha. He was trying to save a little money on this street bike thing since he had just bought a C6 ZR1 when his crazy dad convinced him to buy a street bike too!

As far as tools, I'll put a few links on here of bits similar to what I used. High speed carbide burrs on a die grinder work well once you get the holes drilled. You can even use them on a regular drill, it's just a little harder to control. Another thing that helps is if you have a headband flashlight, so you can shine the light in there and still have both hands free for drilling or grinding. You can't really "hurt" what's inside these mufflers, as long as you don't drill a hole through the outside of the can. lol. I think that would be pretty hard to do actually. Just get in there and hog it out! It doesn't have to be pretty, nobody's going to be looking in there.

Honestly, if the particular part (entire stock exhaust system) wasn't so big and awkward to ship, I'd figure out how I could do this as a service of some sort. Not sure how that would work though, or if it even makes any sense. I'm in the SF Bay Area in case anyone is local to me. Again, not sure how I'd help or what that would even look like.?

Here are some bits similar to what I use...

Long shaft burrs...

Long shaft burr...

Cheap long drill bits...

Cobalt drill bit
 

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This very mod has been around since 2014 ;) Lots of us have done it, one iteration or another. Great job with the pictures. It does make the bike sound much better.
 

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Great pictures man, explained very well.
I know this isn't super loud but I'm bored so... There is a special spot in Hell for you loud D&D muffler havin sumnabitchs. My ears hate riding next to these.
That said, you do you and have fun.
 

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Thanks for the write-up, I want some more noise without being obnoxiously loud. I'll give this a shot. New member, new FZ09 owner, first thread I've seen about this.
 
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