Mod suggestions for ultra-quiet exhaust? - Kawasaki KLR 650 Forum
1987 to 2007 Wrenching & Mods For maintaining, repair or modifications of Generation 1 KLR's. 2007 and earlier.

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post #1 of 12 Old 10-24-2015, 12:56 PM Thread Starter
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Mod suggestions for ultra-quiet exhaust?

I want to try some different modifications to the stock exhaust to try to make even quieter. I have though about welding an external baffle of some sort to end of the muffler, or maybe even try using a second muffler on the other side and running one into the other. Maybe a universal generator muffler or similar.

I am not concerned about a reasonable loss in power, since it has more than I need for the woods I explore in.
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post #2 of 12 Old 10-24-2015, 03:01 PM
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Hello and welcome to the forum!
That's a refreshing switch, most people are always asking how to make their bikes louder!
I don't recall off hand though anyone making a KLR quieter than the stock muffler, hopefully someone will have some suggestions for you.
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post #3 of 12 Old 10-24-2015, 03:18 PM
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Originally Posted by 650Stew View Post
Hello and welcome to the forum!
That's a refreshing switch, most people are always asking how to make their bikes louder!
I don't recall off hand though anyone making a KLR quieter than the stock muffler, hopefully someone will have some suggestions for you.
For real. That's a new one. I don't have any answers for you, but someone will.




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post #4 of 12 Old 10-24-2015, 05:57 PM
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You're breaking new ground here with your request. You'll likely have to try your mods and report back on the result. Remember it's not a Goldwing though. Are you trying to sneak up on deer?
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post #5 of 12 Old 10-24-2015, 09:54 PM
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Do you have restrictions on noise,like a gated community or something? My sister lived in one where they couldn't have a boat or rv in their driveway!
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post #6 of 12 Old 10-25-2015, 05:18 AM
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The exhaust includes gasses flowing in pulses plus sound waves in much shorter pulses. Muting the sound without stopping the gasses is a very complex operation.

The 3 chambers in the KLR muffler each allow the gasses to expand then bleed off through a tube to the next chamber. The expansion/bleed cycle causes the energy to be more disperse and the energy level to be more constant. The stock muffler also has the first chamber lined with fibers (like fiberglass) plus two other fiber-lined sections of tubing. These absorb sound.

Anything you add will have to flow gasses more freely than the stock muffler. Since the gasses have already lost a lot of energy you don't want to add a chamber where they stop entirely.

In particular I'd warn against adding anything that reflects gas pulses or sound waves back toward the muffler exit. Reflecting sound waves is a very effective way to cancel out sound when the reflected wave hits the incoming wave. Not so good for gas pulses.

If you add a chamber to the end of the muffler it'll have to be very large. It will need to get the gases away from the stock exit before any more muffling.

I don't think the exhaust gasses have enough energy to go through another pipe to the other side for a second muffler.

These comments are from my very incomplete understanding of exhaust based on my attempts to quiet a few different bikes. Exhaust is fascinating but very complex.

EDIT: I have an FMF Power Bomb header. I think the KLR Power Bomb is too small to be effective but it's based on a reasonable theory: bleed some exhaust gas into a larger chamber then bleed it back into the main flow. In theory it smears the pulses and can move the powerband higher in the RPM range.* The bulge in the FMF version is really small. Theoretically you can make a larger chamber with small entry and exit (or multiple entries and exits) to further smear the pulses.

* The length from the head to the first expansion chamber is a major factor in tuning an exhaust for a particular RPM. Longer length header tunes for lower RPM; shorter length for higher RPM. The first expansion chamber is the source of the strongest gas pressure waves returning to the valve. When a low-pressure wave returns when the exhaust valve is open then gasses are pulled out. When a high-pressure wave returns when the ex valve is open the gasses don't exit the combustion chamber as easily. Many factory exhausts are designed to be mediocre -- they don't boost any RPM much and they also don't smother other RPMs.

Last edited by Grinnin; 10-25-2015 at 09:19 AM.
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post #7 of 12 Old 10-25-2015, 09:01 AM
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Grinnin brings up some good points. Personally I prefer not to mess with stuff Kawasaki pays their engineers to figure out. Not trying to start a Doohickey discussion either.

I have read about both a KLR 250 and a KLR 650 fitted with dual exhaust. Neither used a dual OEM muffler. Probably something that flows a more freely. Google is your friend on finding that info. I was able to find pictures and forum posts about the conversion on a KLR 250. One of the Moderators at Christian ADV converted his KLR 650 to dual exhaust. Not sure about the long term affects/results from the change.

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post #8 of 12 Old 10-25-2015, 09:21 AM
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Quote:
Originally Posted by klr4evr View Post
I have read about both a KLR 250 and a KLR 650 fitted with dual exhaust. Neither used a dual OEM muffler. Probably something that flows a more freely.
Volume is your friend. With a big enough box you can create a really quiet exhaust that flows all the gasses you can create.
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post #9 of 12 Old 10-26-2015, 09:56 AM
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I doubt you'll find anyone that has done this; I'm sure you're breaking new ground as the stock exhaust is considered very quiet.

You may want to check into the db snorkle; it was originally designed for 2 strokes but may be able to be adapted....biggest issue will be heat. I haven't heard anything about them lately so I'm not sure if they are still in production;

dB Snorkel Silencer - Dirt Bike Parts Review - Dirt Rider Magazine | Dirt Rider

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post #10 of 12 Old 10-26-2015, 02:41 PM
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Is the exhaust noise your whole concern or is other engine noise also a factor?
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