Inside a stock KLR muffler - 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 20 Old 08-28-2016, 01:40 PM Thread Starter
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Inside a stock KLR muffler

Apologies if this is a repost ( feel free to delete), but I didn't find this in any of my searches.

Looking at this you would think the bike would respond in a huge way to a free-flowing muffler, but it seems they don't. Amazing.

http://youtu.be/PJP4cNhzZic
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post #2 of 20 Old 08-28-2016, 09:35 PM
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This is actually really cool, never saw the internals of the KLR can before. Sneaky how they make the gasses and exhaust pulses round all those corners to quiet them down.

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post #3 of 20 Old 08-28-2016, 09:54 PM
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Did ya' notice that his 'Internal' tail pipe outlet sort of looked like a WWII German 'hand gernade'?

Well, my USA model 1987 KLR650-A1 had a 6 inch long / 2 inch O.D. 'Glass-Pac' instead of the "tater-masher"!

I wonder just how many variations of mufflers there could be? His did not have a Catalytic Converter. So, what year and what Country?
Australia is my guess.

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Modify at "YOUR OWN RISK"!

Still riding my 1987 KL650-A1. 84,000+ miles & counting
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post #4 of 20 Old 08-29-2016, 06:25 AM Thread Starter
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How many variations? Well, I tell ya what. You send me a Lexx and I'll gladly fire up the ol' plasma cutter and find out for ya.
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post #5 of 20 Old 08-29-2016, 10:35 AM
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The only reason they don't respond more to a better flowing silencer is because there are worse bottlenecks in the system; the airbox and head to name the two worst....

Dave
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post #6 of 20 Old 08-29-2016, 03:10 PM Thread Starter
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I hear ya. I'm new to these bikes and was amazed at how little improvement could be had from a stock engine. Like you, I'm guessing the head must be ultimate holdback. I'd love to sit down at a flow bench with one....


I'll give Kawasaki props on the muffler, thought. Looking at the internal construction, it's pretty much crush-proof. And full stainless construction is awesome. Kinda hard to complain about a bulletproof muffler that is deadly silent and robs practically 0 hp.

That's twice you've mentioned the air box...I need to check that puppy out...
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post #7 of 20 Old 08-29-2016, 04:59 PM
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Originally Posted by shinyribs View Post
That's twice you've mentioned the air box...I need to check that puppy out...
Don't remember if I posted this before for you or not; KLRCary's testing;

A lot of missunderstanding with airbox issues.

First, the screen. Airflow gains are not linear. Removing the screen with an otherwise stock KLR airbox will only gain you 2 cfm. The engine won't know the differance. However, with a heavily modified airbox, the gain from removing the screen is 8 cfm. Depending on what else is done to the engine, you may make more power. I doubt that you'll feel it, but a dyno will show it. Butt-dyno's can detect very small low rpm changes, but don't detect higher rpm changes very well at all. You'll likely not detect it, but that does not mean it's not there.

Comparing screen removal to other models is wrong, particularly with the newer sportbikes. With them, the screen often serves another purpose as well. Air distribution in a 4 cyl sportbike can be a real problem, particularly with "ram air". Removing the screen on them can cause very real losses, depending on the model. That does NOT apply to the KLR.

Same thing with air filters. There is only about 2 cfm differance from the best filter (UNI), to the worst (K&N). With a modified airbox, that differance grows to 9 cfm.

Here is the flow chart:

Completely stock - 64.8cfm
Same - Remove snorkle - 74cfm
Same - With UNI filter - 76.2cfm
Same - Remove screen - 78.6cfm
Same - Small "L" cut - 85.1cfm
Same - Large "L" cut, open snorkle area further - 92.4
Same - Remove door - 103.2

Alternate - UNI filter, No snorkle, With screen, No door, No "L" cut - 95.4

All at 2" of water, tested at 1 1/2" and 3" and averaged to 2"

To answer the larger question, how much air can the KLR really use?
....................
A stock KLR about 70-80cfm. With a good pipe about 75-90cfm. A modified motor about 90-100cfm. Having a bit more capacity than you you need will not hurt anything. The effects are not linear though. Going from 65cfm to 75cfm you will likely notice, but going from 75 to 85 cfm you likely won't.

Part of the confusion might be due to the effects of the carb shimming. Since that mod is for a stock needle, the snorkle removal serves not just to add air, but to lean out the top end. The stock KLR till 07 is rich on the top. ( The 08 has a smaller main jet.) Airbox mods have much more effect on top end mixture, so, with the stock needle it also helps straighten out the fuel curve.

Finally the airbox door. You've got to carefull there. You don't have clean air there. It's flowing past that door when riding. You can easily create a partial low pressure area there, depending on wind direction, and where you place your leg!

Cary


Clearly the airbox has flow issues! I don't recommend trying to remove the backfire screen (it's a PITA to remove if nothing else) nor running without the airbox door. I'm also not a fan of visible holes in the airbox door or elsewhere. The snorkle and snorkle cover should always be tossed IMO as they do absolutely nothing useful.....after that an L mod or the 4 1" holes help (and also can't hurt). Don't bother with the little push in 1" foam filters as they are counter-productive.

Cheers,
Dave
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post #8 of 20 Old 08-29-2016, 05:15 PM Thread Starter
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That's a really interesting read. Thanks

I wonder how much that applies to low rpm crawling vs someone that commutes on the highway, for example.

When I first got my bike the air box door had about six 1/2" holes drilled in it. Personal opinion, but upwhy drill for fresh air directly under the same side cover as the hot exhaust system?! lol. I sealed those holes up and saw no loss of power, but honestly, I rarely go above 2500-3000 rpm when playing in the woods. I doubt tapping out the available cfm at those engine a speeds, but more power on road is always cool.

The bike really has plenty of power on road for me. And I just came of a 100hp CB... I would like to see more torque, but I understand the motor can only go so slow. I'm loving my 14t sprocket and an eagerly looking forward to getting the KL 600 gearset in there.


I do wonder If any aftermarket exhausts improve low rpm flow enough to warrant the money. You hear a lot about HP claims, but not much on torque curves. I didn't choose a KLR for hp lol...I came here for torque.

Thanks for the info man
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post #9 of 20 Old 08-29-2016, 05:56 PM
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Interesting.

“Take the risk of thinking for yourself , much more happiness , truth, beauty, and wisdom will come to you that way.” Hitchens
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post #10 of 20 Old 08-29-2016, 06:03 PM
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Quote:
Originally Posted by shinyribs View Post
............ I'm loving my 14t sprocket............
I had a 14. That's where you get the biggest bang for your buck. Lights it up under 55 MPH. I just switched back to a 15 after a year. Riding style changed to strictly roads. The 14 was way better on the trail. If I wasn't a 70 MPH rider I'd have kept the 14. A bunch of KLR riders forget about the 14 and it helps a lot with a few minutes worth of effort and very little costs.

“Take the risk of thinking for yourself , much more happiness , truth, beauty, and wisdom will come to you that way.” Hitchens
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