 Lighter Carb Springs
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Joined: Jan 2005
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OP
Oil Expert
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Posts: 2,416 |
Fitted and tried out a pair of Kawasaki gpz900 carb vacuum springs. Same diamater as ours, but lighter and a little shorter. Result - much better throttle response. Maybe this mod is compatible with enlargening the vacuum hole in the slide, but I haven't had the guts to drill that hole yet...  (Mods - maybe something for the Tech Vault? # 92081-1760)
Last edited by piper; 09/27/2008 2:22 AM.
"Wise men speak because they have something to say, fools because they have to say something."
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Re: Lighter Carb Springs
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Joined: Feb 2007
Posts: 23,217 Likes: 61
Fe Butt
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Fe Butt
Joined: Feb 2007
Posts: 23,217 Likes: 61 |
This is an old trick for this type carb. We used to cut the stock spring shorter for a similar result.
You might as well drill the slide if you have the older bike with the smaller hole since later bikes actually come with the larger hole. All you are doing is drilling it to that larger stock size.
I learned all I need to know about life by killing smart people and eating their brains.
Eat right ,Exercise ,Stay fit, Die Anyway!
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Re: Lighter Carb Springs
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Joined: Aug 2007
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Should be Riding
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Should be Riding
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I agree with Ian, if you can change the springs, you can drill the slide. Its very easy to do, with pics from the tech vault.
Always remember to be yourself. Unless you suck. Then pretend to be someone else.
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Re: Lighter Carb Springs
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Joined: Feb 2005
Posts: 988
3/4 Throttle
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3/4 Throttle
Joined: Feb 2005
Posts: 988 |
OK, I remember hearing that there are other springs out there that are lighter than ours that will work. Was it from a Yamaha? or something else. I would like to try this mod as well, should be a cheap mod. Year of the GPZ 900 springs that you used will work too.
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Re: Lighter Carb Springs
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Joined: Jan 2005
Posts: 2,416
Oil Expert
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OP
Oil Expert
Joined: Jan 2005
Posts: 2,416 |
The # is 92081-1760. Hope this helps.
"Wise men speak because they have something to say, fools because they have to say something."
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Re: Lighter Carb Springs
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Joined: Feb 2005
Posts: 988
3/4 Throttle
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3/4 Throttle
Joined: Feb 2005
Posts: 988 |
Thanks, I will give it a try. 
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Re: Lighter Carb Springs
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Joined: Aug 2007
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Should be Riding
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Should be Riding
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I am going to try them out, too
Always remember to be yourself. Unless you suck. Then pretend to be someone else.
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Re: Lighter Carb Springs
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Joined: Aug 2007
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Should be Riding
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Should be Riding
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So I finally got my carb springs installed today.... wow, what a difference! The throttle response is much, much quicker now, even when I just blip the throttle. I think they cost about 30 bucks from the Kawasaki dealer. For me, worth the price.
Always remember to be yourself. Unless you suck. Then pretend to be someone else.
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Re: Lighter Carb Springs
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Joined: Jul 2007
Posts: 6,060 Likes: 6
Worn Saddle
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Worn Saddle
Joined: Jul 2007
Posts: 6,060 Likes: 6 |
Quote:
So I finally got my carb springs installed today.... wow, what a difference! The throttle response is much, much quicker now, even when I just blip the throttle. I think they cost about 30 bucks from the Kawasaki dealer. For me, worth the price.
I can see where this is going. 904 kit, lighter carb springs, louder exhaust.... Whatta ya got in mind, Dave? 
Fidelis et Fortis
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Re: Lighter Carb Springs
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Joined: Aug 2007
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Should be Riding
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Should be Riding
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I'm trying to hit the "H" on the speedometer.... go look at it and you'll know what I mean 
Always remember to be yourself. Unless you suck. Then pretend to be someone else.
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Re: Lighter Carb Springs
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Joined: Jul 2007
Posts: 6,060 Likes: 6
Worn Saddle
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Worn Saddle
Joined: Jul 2007
Posts: 6,060 Likes: 6 |
So, when did you start looking at your speedometer? After our last ride, I didn't think you cared! 
Fidelis et Fortis
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Re: Lighter Carb Springs
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Joined: Aug 2007
Posts: 10,728 Likes: 5
Should be Riding
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Should be Riding
Joined: Aug 2007
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Dude! You talk as if I have some sort of disregard for posted speed limits on the interstate! Actually, I do use them as a sort of "guideline", if you will. 
Always remember to be yourself. Unless you suck. Then pretend to be someone else.
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Re: Lighter Carb Springs
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Joined: Jul 2007
Posts: 6,060 Likes: 6
Worn Saddle
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Worn Saddle
Joined: Jul 2007
Posts: 6,060 Likes: 6 |
Quote:
Dude! You talk as if I have some sort of disregard for posted speed limits on the interstate!
Actually, I do use them as a sort of "guideline", if you will.
Yep
Fidelis et Fortis
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Re: Lighter Carb Springs
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Joined: Aug 2007
Posts: 10,728 Likes: 5
Should be Riding
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Should be Riding
Joined: Aug 2007
Posts: 10,728 Likes: 5 |
Always remember to be yourself. Unless you suck. Then pretend to be someone else.
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Re: Lighter Carb Springs
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Joined: Jul 2007
Posts: 6,060 Likes: 6
Worn Saddle
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Worn Saddle
Joined: Jul 2007
Posts: 6,060 Likes: 6 |
Wow! A 7 gal reserve tank?!! My poor, old bum would never recover!
Fidelis et Fortis
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Re: Lighter Carb Springs
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Joined: Aug 2007
Posts: 10,728 Likes: 5
Should be Riding
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Should be Riding
Joined: Aug 2007
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Yeah, I think 3 gallons would be just about right. 250-300 miles at a time would be long enough.
Always remember to be yourself. Unless you suck. Then pretend to be someone else.
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Re: Lighter Carb Springs
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Joined: Jan 2005
Posts: 2,416
Oil Expert
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OP
Oil Expert
Joined: Jan 2005
Posts: 2,416 |
Quote:
So I finally got my carb springs installed today.... wow, what a difference! The throttle response is much, much quicker now, even when I just blip the throttle.
Yup. Same here. Easy, cheap mod with great results. 
"Wise men speak because they have something to say, fools because they have to say something."
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Re: Lighter Carb Springs
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Joined: Apr 2007
Posts: 286
Adjunct
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Adjunct
Joined: Apr 2007
Posts: 286 |
This is why I love this site. Great inexpensive performance tips which make our bikes run better. Anyone out there cut down the stock spring and if so by how much and how did it work out? Love the idea of making simple mods to improve these bikes. Right now running a drilled airbox, Uni filter, short TORs, #125 main jets and TBS needles on a 2007 America.
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Re: Lighter Carb Springs
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Joined: Jul 2008
Posts: 1,440
Learned Hand
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Learned Hand
Joined: Jul 2008
Posts: 1,440 |
Quote:
The throttle response is much, much quicker now, even when I just blip the throttle.
That gives me an idea. Now, I know it's kinda off the wall, but hear me out. What if we use carbs that have the throttle linkage connected directly to the slides? Would that work? Then you could get rid of the springs entirely. Danm, I'm smart. Think I'll patent that...
'08 America Blue/White; Custom Headlamps, Custom Lowers, Clearview 20", Bafflectomy
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Re: Lighter Carb Springs
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Joined: Sep 2005
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Freelance Jedi Knight
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Freelance Jedi Knight
Joined: Sep 2005
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buy keihin CR Special and you are done
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Re: Lighter Carb Springs
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Joined: Feb 2008
Posts: 2,671 Likes: 15
Loquacious
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Loquacious
Joined: Feb 2008
Posts: 2,671 Likes: 15 |
[quote... Think I'll patent that...
You outta throw a smiley or two in there, as others might think you're serious...
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Re: Lighter Carb Springs
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Joined: May 2008
Posts: 619
Adjunct
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Adjunct
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There is a fine line on this that could cause problems. On my Ninja the carb (Keihin) springs were too weak and the engine surged at a constant throttle position. Stretching them some at least temporarily fixed that but was annoying when it was happening. Old Triumph mechanic gave me that hint.
Long time observer of the human condition.
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Re: Lighter Carb Springs
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Joined: Feb 2007
Posts: 23,217 Likes: 61
Fe Butt
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Fe Butt
Joined: Feb 2007
Posts: 23,217 Likes: 61 |
Quote:
Quote:
The throttle response is much, much quicker now, even when I just blip the throttle.
That gives me an idea. Now, I know it's kinda off the wall, but hear me out. What if we use carbs that have the throttle linkage connected directly to the slides? Would that work? Then you could get rid of the springs entirely. Danm, I'm smart. Think I'll patent that...
The easy answer is yes and it has been done. I have been toying with using a set of Amal carbs I have from a Norton 850 Commando. I restored the Norton for a customer and ity only had 6,000 original miles on it. was a sweet bike but had been sitting for 20+ years and everything was gummed up.
I learned all I need to know about life by killing smart people and eating their brains.
Eat right ,Exercise ,Stay fit, Die Anyway!
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Re: Lighter Carb Springs
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Joined: Feb 2008
Posts: 2,671 Likes: 15
Loquacious
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Loquacious
Joined: Feb 2008
Posts: 2,671 Likes: 15 |
Quote:
... The easy answer is yes and it has been done...
Old school. That used to be the norm.
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Re: Lighter Carb Springs
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Joined: Feb 2008
Posts: 2,671 Likes: 15
Loquacious
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Loquacious
Joined: Feb 2008
Posts: 2,671 Likes: 15 |
Quote:
...Easy, cheap mod with great results...
How does it hold a steady cruise in the 2-3k range in 2nd gear?
My personal opinion is the stock springs are too stiff, yet I have to wonder if a stock cut-down spring or a lighter rate replacement is the way to go with the stock CVK's.
Cut springs still have the same basic spring rate, & lighter replacements may be too light for a steady cruise.
Those Mik 42's may be on my agenda at some point.
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Re: Lighter Carb Springs
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Joined: Aug 2007
Posts: 10,728 Likes: 5
Should be Riding
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Should be Riding
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I noticed no ill-affects on the highway, I don't spend a lot of time in the 2-3k range in 2nd gear
Always remember to be yourself. Unless you suck. Then pretend to be someone else.
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Re: Lighter Carb Springs
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Joined: Feb 2008
Posts: 2,671 Likes: 15
Loquacious
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Loquacious
Joined: Feb 2008
Posts: 2,671 Likes: 15 |
Quote:
...I don't spend a lot of time in the 2-3k range in 2nd gear
Understood, & most of us wouldn't either, however if there is an issue with light springs it would likely be detected in that situation.
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Re: Lighter Carb Springs
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Joined: Apr 2007
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Adjunct
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Adjunct
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Good points gentlemen. Surging at steady throttle would not be good. Sounds like no one has had that issue with the Kawi springs so far. But in the interest of cheapness, cuting the stock spring would be free, so I'm wondering if anyone has done it and how much did they cut off and how did it work out? Anyone?
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Re: Lighter Carb Springs
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Joined: Feb 2007
Posts: 23,217 Likes: 61
Fe Butt
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Fe Butt
Joined: Feb 2007
Posts: 23,217 Likes: 61 |
I wonder if it would make the mixture too rich at mid throttle. My thinking is the lighter spring will allow the slide open a little farther at any given throttle position where the slide is in play thus acting as if there was a slightly larger jet due to the needle being open farther.
I learned all I need to know about life by killing smart people and eating their brains.
Eat right ,Exercise ,Stay fit, Die Anyway!
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Re: Lighter Carb Springs
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Joined: Jul 2008
Posts: 1,440
Learned Hand
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Learned Hand
Joined: Jul 2008
Posts: 1,440 |
Quote:
I wonder if it would make the mixture too rich at mid throttle. My thinking is the lighter spring will allow the slide open a little farther at any given throttle position where the slide is in play thus acting as if there was a slightly larger jet due to the needle being open farther.
I don't see how that could make it richer. At the same time the needle is pulled up, the slide is opening to allow more air. Seems to me that the possibility of surging (or total loss of control) is the only downside.
'08 America Blue/White; Custom Headlamps, Custom Lowers, Clearview 20", Bafflectomy
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Re: Lighter Carb Springs
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Joined: Jul 2008
Posts: 1,440
Learned Hand
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Learned Hand
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OK, now I have another idea. One could lighten the spring to the point where throttle response is virtually instantaneous. It'll surge like crazy. The solution is to attach a miniature hydraulic dampener to the slide. Danm, I'm smart. Think I'll patent that.
'08 America Blue/White; Custom Headlamps, Custom Lowers, Clearview 20", Bafflectomy
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Re: Lighter Carb Springs
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Joined: Feb 2008
Posts: 2,671 Likes: 15
Loquacious
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Loquacious
Joined: Feb 2008
Posts: 2,671 Likes: 15 |
Quote:
...The solution is to attach a miniature hydraulic dampener to the Danm, I'm smart. Think I'll patent that.
Given that a "dampener" makes things wet, why would you want to do that? 
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Re: Lighter Carb Springs
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Joined: Feb 2007
Posts: 23,217 Likes: 61
Fe Butt
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Fe Butt
Joined: Feb 2007
Posts: 23,217 Likes: 61 |
Quote:
Quote:
I wonder if it would make the mixture too rich at mid throttle. My thinking is the lighter spring will allow the slide open a little farther at any given throttle position where the slide is in play thus acting as if there was a slightly larger jet due to the needle being open farther.
I don't see how that could make it richer. At the same time the needle is pulled up, the slide is opening to allow more air. Seems to me that the possibility of surging (or total loss of control) is the only downside.
Because the slide and needle could be open at a slower RPM given that less vacuum is needed to open them thus supplying more A/F than required for that given RPM.
I learned all I need to know about life by killing smart people and eating their brains.
Eat right ,Exercise ,Stay fit, Die Anyway!
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Re: Lighter Carb Springs
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Joined: Aug 2007
Posts: 10,728 Likes: 5
Should be Riding
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Should be Riding
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Posts: 10,728 Likes: 5 |
How about as soon as I get my valves adjusted (very soon), I go get another dyno run and post my air/fuel mix for everyone to judge for themselves.
Always remember to be yourself. Unless you suck. Then pretend to be someone else.
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Re: Lighter Carb Springs
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Joined: Feb 2007
Posts: 23,217 Likes: 61
Fe Butt
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Fe Butt
Joined: Feb 2007
Posts: 23,217 Likes: 61 |
sounds good, I wasn't saying this was the case, just a thought. I have never personally played with carb springs since I have always had cable operated slides until this bike.
I learned all I need to know about life by killing smart people and eating their brains.
Eat right ,Exercise ,Stay fit, Die Anyway!
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Re: Lighter Carb Springs
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Joined: Aug 2007
Posts: 10,728 Likes: 5
Should be Riding
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Should be Riding
Joined: Aug 2007
Posts: 10,728 Likes: 5 |
yeah, I just can't afford those nice 42mm mikuni's right yet, so this makes for a decent compromise
Always remember to be yourself. Unless you suck. Then pretend to be someone else.
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Re: Lighter Carb Springs
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Joined: Jul 2008
Posts: 1,440
Learned Hand
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Learned Hand
Joined: Jul 2008
Posts: 1,440 |
Quote:
Quote:
Quote:
I wonder if it would make the mixture too rich at mid throttle. My thinking is the lighter spring will allow the slide open a little farther at any given throttle position where the slide is in play thus acting as if there was a slightly larger jet due to the needle being open farther.
I don't see how that could make it richer. At the same time the needle is pulled up, the slide is opening to allow more air. Seems to me that the possibility of surging (or total loss of control) is the only downside.
Because the slide and needle could be open at a slower RPM given that less vacuum is needed to open them thus supplying more A/F than required for that given RPM.
Ah, I see what you mean. Still, I think a case could be made for just the oposite effect. If the slide opens early, air velocity might not be sufficient to pull the additional fuel needed to maintain proper mix from the metering circuit. In that case, it would run lean. It will be interesting to see the dyno results on this mod.
'08 America Blue/White; Custom Headlamps, Custom Lowers, Clearview 20", Bafflectomy
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Re: Lighter Carb Springs
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Joined: Feb 2008
Posts: 2,671 Likes: 15
Loquacious
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Loquacious
Joined: Feb 2008
Posts: 2,671 Likes: 15 |
Quote:
...I think a case could be made for just the oposite effect. If the slide opens early, air velocity might not be sufficient to pull the additional fuel needed to maintain proper mix from the metering circuit. In that case, it would run lean...
Jack, I don't follow that logic. The only place this should even be a concern is on low speed transition, in which case the elevated slide/needle theoretically caused by a too-light spring could induce a transient rich condition. And that is just theoretical. Presuming the Kawi lighter springs maintain sufficent tension then it won't matter, or it won't matter enough to be of concern. I doubt that a dyno run with this mod is going to reveal anything remarkable regarding A/F, provided the springs have enough rate in them.
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Re: Lighter Carb Springs
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Joined: Jan 2005
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Worn Saddle
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Worn Saddle
Joined: Jan 2005
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Bucky , f.k.a. Martin, has one of these big tanks, used to be on his America. Drop him a PM maybe he still has it and would give you a deal if he wants to sell it.
A word to the wise is not necessary. It is the stupid ones who need the advice.
Pat
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Re: Lighter Carb Springs
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Joined: Feb 2008
Posts: 2,671 Likes: 15
Loquacious
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Loquacious
Joined: Feb 2008
Posts: 2,671 Likes: 15 |
I ordered the Kawi springs, stay tuned.
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