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Last 007 MOM
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Discussion Starter · #1 ·
I have read several threads over the last year or so about removing the secondary butterflies. I guess by doing so it eliminates some hesitation, but what was the original intent for those butterflies, what were they supposed to do to begin with, was it a smog or detune issue? Inquiring minds want to know.
 

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Millenium Vulcan Pilot
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3,808 Posts
I'm not positive, but I was told that they were put there to smooth out the acceleration. This would help with newbie riders who would try to crank her wide open too early in the rpm range I think.

I know if I crank on her too early with the Butterflies removed I can make her stumble before she catches and takes off.

But before I removed the butterflies, I don't think I had that problem.

But any of us experienced riders know when to crank and when not crank her wide open would never have that problem, with or without butterflies.

I took them out, no diff on gas mileage, maybe a tad quicker response to acceleration but not mind boggling. You won't have to hold on any tighter...:lol:

I'll be interested to hear if they were there for some other reason.

And Merry Christmas to you and yours, Lobo.
 

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I'm your Huckleberry
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3,316 Posts
:confused:

Ummm...perhaps someone could explain exactly what these are? On a carburetor (for a car at least)...the secondary butterflies are there to prevent too much airflow when the engine doesn't need it (just like the primary butterflies). Taking them out would kill performance...not to mention any sense of driveability.

So what exactly are we talking about here?
 

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Last 007 MOM
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9,198 Posts
Discussion Starter · #4 ·
I'm not positive, but I was told that they were put there to smooth out the acceleration. This would help with newbie riders who would try to crank her wide open too early in the rpm range I think.

I know if I crank on her too early with the Butterflies removed I can make her stumble before she catches and takes off.

But before I removed the butterflies, I don't think I had that problem.

But any of us experienced riders know when to crank and when not crank her wide open would never have that problem, with or without butterflies.

I took them out, no diff on gas mileage, maybe a tad quicker response to acceleration but not mind boggling. You won't have to hold on any tighter...:lol:

I'll be interested to hear if they were there for some other reason.

And Merry Christmas to you and yours, Lobo.
Thanks, Mike.

I never get after mine hard in the first couple of gears anyway, but on occassion 3rd, 4th, and 5th get a little workout ... just enough to convince my brother on his GL to back off :swave:

Have a very Merry Christmas Mike and thanks again for the response.
 

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Last 007 MOM
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9,198 Posts
Discussion Starter · #5 ·
:confused:

Ummm...perhaps someone could explain exactly what these are? On a carburetor (for a car at least)...the secondary butterflies are there to prevent too much airflow when the engine doesn't need it (just like the primary butterflies). Taking them out would kill performance...not to mention any sense of driveability.

So what exactly are we talking about here?
It seems there are two sets of butterfies for some injected models. I have read where some of the guys have taken the second set out and it helps with acceleration. As Mike indicates above it could be to help keep the beast from getting to carried away to fast. I really don't know what the original purpose was for those to begin with, or if removal could create issues anyplace else in the performance. I am still curious.
 

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I'm your Huckleberry
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3,316 Posts
It seems there are two sets of butterfies for some injected models. I have read where some of the guys have taken the second set out and it helps with acceleration. As Mike indicates above it could be to help keep the beast from getting to carried away to fast. I really don't know what the original purpose was for those to begin with, or if removal could create issues anyplace else in the performance. I am still curious.
Two sets in the same air tract?? Or something like that? Interesting...weird but interesting. I'll have to look into it...
 

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I'm your Huckleberry
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3,316 Posts
Two sets in the same air tract?? Or something like that? Interesting...weird but interesting. I'll have to look into it...
Never mind...just found an old post and Rich described it...

That seems kinda similar to the old Quadrajet secondaries...mechanically opened bottoms and vacuum opened tops. Never seen anything like that on a fuel injected motor though. :confused:
 

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Giant Biker
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2,323 Posts
Never mind...just found an old post and Rich described it...

That seems kinda similar to the old Quadrajet secondaries...mechanically opened bottoms and vacuum opened tops. Never seen anything like that on a fuel injected motor though. :confused:

I know some of the recent Mustangs used a similar setup. A lot of people would pull the secondaries, which helped on the strip but hurt a little bit in around town driveability.
 

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Giant Biker
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2,323 Posts
It seems there are two sets of butterfies for some injected models. I have read where some of the guys have taken the second set out and it helps with acceleration. As Mike indicates above it could be to help keep the beast from getting to carried away to fast. I really don't know what the original purpose was for those to begin with, or if removal could create issues anyplace else in the performance. I am still curious.
My local Kawi mechanic says they are there to keep sudden throttle movement from making the engine stumble. I also think they are there as a bit of a de-tune, but that is just my opinion.

The only time I have an issue without the butterflies is when I try to go full throttle straight from idle. She will cough then. Otherwise, I seem to get much quicker response, and the removal stopped the random hesitation I was getting. I am pretty sure the secondaries were sticking closed occassionally.
 

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Giant Biker
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2,323 Posts
I wonder if a good alternative might not be to drill some 1/8" holes in them?

I don't know. I took them out as a test for my issue. The bike would just choke randomly, and after a second or 2, it would come to life. It was suggested to me that the secondaries might be sticking, so I took them out. No more hesitation, no more choking when trying to get going, plus increased performance.

Bike seems to need to warm up a bit more in colder weather, but no big deal.
 

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Slow Guy on a Fast Bike
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25,197 Posts
I too removed them just to see. My butt dyno seemed to feel an increase in acceleration, and I haven't noticed either any hesitation or any issues with cold weather starting.

As it takes all of 10 minutes to remove them (just don't lose that little screw into the intake!!!!!!) I didn't see any reason not to at least try.
 

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Registered
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3 Posts
I have read several threads over the last year or so about removing the secondary butterflies. I guess by doing so it eliminates some hesitation, but what was the original intent for those butterflies, what were they supposed to do to begin with, was it a smog or detune issue? Inquiring minds want to know.
I saw a video the other day from a British guy said that it's not good to take the secondary butterflies out. I forget exactly how he worded it but In a sense what they do is the restrict the air going inside the throttle body because there's no way to dynamically change the size of the ports in the throttle body between the low and high RPM range
 

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Registered
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1,260 Posts
I believe it's a two stage system to not overload the bike with too much air, so the bike doesn't stall. Something that would be more of a problem on a cold engine I would think. I don't like to remove components like this. The engineeers aren't idiots. Unless you opt for new carbs, or have to rejet them for an exhaust, I just keep them clean inside and out. My 2 cents worth. :)
 
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