sputter exhaust sound while maintaining speed

mgdaubo

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Hello all. I tried searching but not much people talking about this issue.

Mine is 2005 model, everything is stock except the exhaust with straight pipes mod and CAT removed. It accelerates and run fine. But while maintaining constant speed or slight deacceleration the exhaust sound sputters like a discontinuous beat sound. This happens while cruising around 3K to 5k rpm, maybe at higher rpm it is still there but I cannot hear because the beat increases proportional to rpm and it is too high to hear. I don't really feel any jerky, it is just the annoying exhaust sound. Look like it gives this sound whenever the engine has no load or light load.

The best discussion I can find is here, it is about FZ09 and it seems to be fixed by a ECU map: Help! bike has a sputter. running out of ideas! - Page 5

My questions: is this normal? anyone have this issue? what is the root cause and any idea to reduce it apart from trying other ECU maps?
 

TownsendsFJR1300

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"Straight pipes mod" as in NO muffler at all?? Basically just the header out a long or short straight pipe?

A video posted might help, but if there's NO back pressure at all, that may be your issue.. "Leaning out".


To your question itself, I have open Scorps, Cat still installed. The engine runs super smooth, no sputtering, backfiring.
 
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mgdaubo

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"Straight pipes mod" as in NO muffler at all?? Basically just the header out a long or short straight pipe?

A video posted might help, but if there's NO back pressure at all, that may be your issue.. "Leaning out".
Yes, the pipe is branched to 2 smaller grid pipes (around 30mm diameter) wrapped by fiber glass then go straight out. This was done by previous owner. The sound is not good but it's not the time for it now.

I smell rich exhaust gas when cold start and during warming up. When it is fully warm the smell gone. There is no or very less pop or backfiring, only if I ride very hard, so I don't know if it is running lean or not.

I will plan for recording a video.

To your question itself, I have open Scorps, Cat still installed. The engine runs super smooth, no sputtering, backfiring
Thanks for your sharing.

Can the AIS cause this annoying sound?
I remember somewhere on this forum somebody was telling about a leak on the pipes can cause strange sound, but now I could not find that post.
 

TownsendsFJR1300

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Yes, the pipe is branched to 2 smaller grid pipes (around 30mm diameter) wrapped by fiber glass then go straight out. This was done by previous owner. The sound is not good but it's not the time for it now.

I smell rich exhaust gas when cold start and during warming up. When it is fully warm the smell gone. There is no or very less pop or backfiring, only if I ride very hard, so I don't know if it is running lean or not.

I will plan for recording a video.


Can the AIS cause this annoying sound?
I remember somewhere on this forum somebody was telling about a leak on the pipes can cause strange sound, but now I could not find that post.

Never heard of he AIS causing the sound.

You may want to check your header NUTs at the head for tightness. I had several of mine loosen up and make an odd sound.
If you can, feel round the header and the head when idling (rev it some ) checking for any leakage.

Your exhaust seems to be about the same size of my open Scorp as well...
 
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mgdaubo

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So here is the video: https://www.youtube.com/watch?v=Rf9y18LNy3g

I mount my phone on the rear grab handle. Sorry the sound quality is not so good and the camera is looking toward sky.
You can hear the sputter sound when I was maintaining constant speed, it was 2nd gear, 2500 ~ 3500 rpm, speed around 30-40km/h. The bike is not jerking.
Whenever I accelerate, the sputter sound gone, then it comes back when I decelerate and maintain constant speed.

I have just checked the head pipe nuts, they are all tight.

Any idea?
 
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mgdaubo

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Your bike sounds normal.

Mine sounds the same at the lower RPM's.

Go ride!!!!!

Thanks Scott,

Happy to hear it is normal.

But it is still quite annoy since most of the time I will be cruising in city with that sound. The traffic here will not allow me to rev more than 5000 rpm so often. In certain traffic conditions I usually slightly accelerate then use clutch to cruise to avoid this odd sound, but it is not convenient all the time.

Does the stock exhaust sound like this?

Anyway, happy new year to you all :)
 

TownsendsFJR1300

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With the stock exhaust, the bike is super quiet and sounds like a sewing machine.

As noted earlier, yours sounds pretty close to mine (at least at those RPM's). If like mine, over 5,000 RPM's, it screams and sounds like a "go fast" liter bike.
I can put DB killers in mine to quiet it down, but if your exhaust is home made, you may have to get /make up, etc a baffle to quiet it down...

Re-installing the CAT may quiet it down some. I left mine on as I didn't want it any louder (and didn't have any issues what so ever).

Your video clip didn't sound too loud to me. If under light throttle and little load, you can cruise at 3k, that'd be a little quieter.

I usually shift at around 4K in town...


 
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mgdaubo

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With the stock exhaust, the bike is super quiet and sounds like a sewing machine.

As noted earlier, yours sounds pretty close to mine (at least at those RPM's). If like mine, over 5,000 RPM's, it screams and sounds like a "go fast" liter bike.
I can put DB killers in mine to quiet it down, but if your exhaust is home made, you may have to get /make up, etc a baffle to quiet it down...

Re-installing the CAT may quiet it down some. I left mine on as I didn't want it any louder (and didn't have any issues what so ever).

Your video clip didn't sound too loud to me. If under light throttle and little load, you can cruise at 3k, that'd be a little quieter.

I usually shift at around 4K in town...

Mine sounds screaming at over 5000 rpm, and in town I shift at 4000 rpm, too.
So I guess I will live with this sputter sound at low rpm.

I've just measure again my pipes, they are 40mm diameter. Actually I want the sound a little bit quieter, so maybe I will try some silencer to reduce the opening to 30mm.

Thank you again, Scott.
Happy new year :)
 

ShoopCE

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I agree with Scott. I think that sound is fairly normal.

I have a stock muffler that a previous owner partially gutted. He did a good job and the sound is nicer and deeper and doesn't sound like an open can. I also get that sputter sound when backing off of the throttle. I call it a chuckle and sort of like that sound. The chuckle or sputter might be enhanced because you have very little back pressure on the pipes. Same but less so for Scott's or my bike. I don't know if a bike with a stock pipe will make that sound, so this is just a theory.

If the lack of back pressure causes this sound then a diameter restriction will increase the back pressure and that might reduce the sputter a bit. A simple diameter restriction will not reduce the sound volume very much.

Good luck!

Chris
 

TownsendsFJR1300

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I suspect with the stock exhaust that the sound is still there, you just can't hear it.

I put aftermarket pipes on a B-King years ago and it made a similar sound at low cruising
RPM's. (That thing was a BEAST-ugly, but FAST...)
 
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