Popping on deceleration - Kawasaki KLR 650 Forum
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post #1 of 5 Old 09-10-2013, 04:39 PM Thread Starter
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Popping on deceleration

I've noticed my KLR makes a popping sort of noise on decelleration if I'm engine braking (none if I hold the clutch in). Basically mini-backfiring sort of noises, I'm guessing.

The bike has an FMF exhaust and I was told the carburetor was rejetted when that was installed.

A) is this bad for the bike?

B) does this mean the exhaust is bad?

I've searched a bit, but threads coming back are from pre -07 bikes, mine is an '09.
More puzzlingly, seemed to talk about the carburetor, which I wouldn't think would even be in the equation on deceleration. But on that note, again, my understanding is the carb was rejetted when the FMF exhaust was put on.
If this is the case, would using higher octane gas help? (I'm thinking lean = detonation, which higher octane gas prevents)

Obviously I'm totally unclear what this issue is (if it's even an issue), and how the carburetor would be involved, so ignore my mental wanderings if totally irrelevant or if I'm walking down the wrong train track.

Please advise, thanks!
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post #2 of 5 Old 09-10-2013, 06:01 PM
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Originally Posted by geolemon View Post
I've noticed my KLR makes a popping sort of noise on decelleration if I'm engine braking (none if I hold the clutch in). Basically mini-backfiring sort of noises, I'm guessing.

The bike has an FMF exhaust and I was told the carburetor was rejetted when that was installed.

A) is this bad for the bike?

B) does this mean the exhaust is bad?

I've searched a bit, but threads coming back are from pre -07 bikes, mine is an '09.
More puzzlingly, seemed to talk about the carburetor, which I wouldn't think would even be in the equation on deceleration. But on that note, again, my understanding is the carb was rejetted when the FMF exhaust was put on.
If this is the case, would using higher octane gas help? (I'm thinking lean = detonation, which higher octane gas prevents)

Obviously I'm totally unclear what this issue is (if it's even an issue), and how the carburetor would be involved, so ignore my mental wanderings if totally irrelevant or if I'm walking down the wrong train track.

Please advise, thanks!

Decel popping is a lean conditon not a detonation problem. A KLR is a relatively low combustion pressure engine so higher octane is wasted.

When you close the throttle there is vacuum created and the pilot mixture is sucked into the cylinder. If the mixture is lean the excessive exhaust heat ignites that gas causing popping. Some popping is normal.

Check the exhaust header to cylinder connection and the muffler to end pipe connection. Air leaks in either of those 2 areas will cause decel popping.

If those are OK turn out the air screw some more.

People have removed the air injection system also to cure excessive decel popping.

No eye has seen, no ear has heard, no mind has conceived what God has prepared for those who love him. 1 Cor 2:9

Last edited by Spec; 09-10-2013 at 06:04 PM.
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post #3 of 5 Old 09-10-2013, 06:55 PM
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Agree with Spec. That and I wouldn't be surprised if the PO put on the pipe and didn't touch the carb. Whats your MPG? You can be too lean and get bad mpg as well.

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post #4 of 5 Old 09-10-2013, 11:04 PM Thread Starter
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MPG seems really good - between 50mpg and 55mpg, and I still get off a bit on ripping away from stops... first bike you know.

I'll check the pipe connections, because I do swear that it's gotten slightly louder, and I did have an incident where I was riding with a girl on the back when I had the 2" lowering links in, and the tire was rubbing on the muffler.

I just went for a ride tonight, and tried to make it pop... it only happens under these conditions:
Downshift (to engine brake) and let off the clutch.
Accelerate quickly and then let off the throttle quickly.
It doesn't do it if I'm at a pretty well speed-matched RPM (cruising) and just let off the throttle to slow down gradually.
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post #5 of 5 Old 09-11-2013, 06:45 AM
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A little popping on decal is good.

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