June 5th, 2014, 07:50 AM | #1 |
dirty boy
Name: Joe
Location: Johnstown, PA
Join Date: Sep 2012 Motorcycle(s): I don't even know anymore?? Posts: A lot.
MOTM - Apr '14
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Lets talk carbs and carb mods
Ok tuners educate me.
Is there much of a point in doing carb mods say boring, or just going to a larger carb with out making changes else where? would you see gains with a larger carb while using the stock intake cams, timing and valves? Are you going to get any more air in with larger carbs or simply get about the same volume air in with different velocities with out making changes else where? could you change the vacuum pressure to suck in more air? is that possible? is this a good idea? would this be difficult? if you are going to use larger carbs what additional mods would you use to complement the larger carb for best gains? Those are the questions I have for now...
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I love the smell of burning pre-mix in the morning I don't think I'm a lot dumber than you thought that I think that I thought I was once. |
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June 5th, 2014, 08:00 AM | #2 | |
ninjette.org member
Name: oswaldo
Location: Clarksville,Tn
Join Date: Jun 2013 Motorcycle(s): 2010 Kawasaki Ninja 250R (Passion Red, Ca Model) Posts: 107
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I would be rich by now if I had a dollar for every person that has told me "You need to upgrade, You need a bigger bike, You need more power..." |
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June 5th, 2014, 08:26 AM | #3 |
ninjette.org certified postwhore
Name: Eric
Location: Iowa City
Join Date: May 2009 Motorcycle(s): 2008 Kawmeracchi 350 2010 Project X Posts: A lot.
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MOTM - Sep '18, Feb '16
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The stock carbs are very good. I made as much as 34 hp with them. I did not see a drastic change going to. 31mm carbs. I made many changes to the engine and timing changes compression and exhaust changes. The stock carbs never seemed to be a problem. Time consuming to re jet com paired to race carbs. But flow wise they are very good.
A bigger carb without a major increase in engine volumetric efficiency causes the air to slow down. It has been proven more air And fuel will enter a combustion if the air fuel mix has greater velocity. So larger carb on a stock engine will have a negative effect on performance.
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Top speed 123.369mph. Ohio mile Worlds fastest 250 ninja |
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June 5th, 2014, 08:44 AM | #4 |
ninjette.org sage
Name: Alex
Location: Ebensburg, PA
Join Date: Sep 2013 Motorcycle(s): 2015 Yamaha FZ07, Ninja 250r 2012 Limited Edition (Sold) Posts: 529
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Didn't you say like 3 days ago you were done modding the Ninja for while?
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June 5th, 2014, 08:48 AM | #5 |
dirty boy
Name: Joe
Location: Johnstown, PA
Join Date: Sep 2012 Motorcycle(s): I don't even know anymore?? Posts: A lot.
MOTM - Apr '14
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^yes, but that doesn't mean I can't plan for the future
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I love the smell of burning pre-mix in the morning I don't think I'm a lot dumber than you thought that I think that I thought I was once. |
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June 5th, 2014, 11:01 AM | #6 |
ninjette.org sage
Name: bruce
Location: northern illinois
Join Date: Jan 2012 Motorcycle(s): Race bikes:08 Ninja 250,11 R6,16 ZX6,SV650.3 HD-1947,2-2003,2010. 1946 Indian and a lot of dirt bikes.2 Posts: 999
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The factory carbs are a compromise of drivability,emmissions, fuel economy and performance. Thus they are not a great performance carb. They may be a good performance carb but you will never tune them to FCR standards. Keep in mind that Kawasaki has to entertain many when selling a bike not just the performance guys. They have to make it ridable for all levels of rider, make it get acceptable fuel economy and keep Uncle Sam happy for emmission purposes. I am confident that given the same bike I could tune it for more power output with a set of 31mm FCR carbs than with the stockers.
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June 5th, 2014, 11:08 AM | #7 |
Ms. Personality
Name: CB
Location: Murvill, TN
Join Date: Jan 2009 Motorcycle(s): Depends on the week you ask Posts: A lot.
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Polishing is pretty much the best thing you can do to stock carbs. Bigger sized carbs can be used but generally you have to fiddle around with the jetting (duh) and they don't really do a ton of good unless you have bigger valves, cam work, port and polish the motor, etc... I think the limiting factor on these motors is the motors not the carbs but now I'm rambling Ducati. Also... Look into car carbs. I know Weber made some sidedraught carbs that I have seen hooked up to motorcycles. I'm not sure if they did that for parts availability or what.
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June 10th, 2014, 07:03 PM | #8 | |
Board Member
Name: ...
Location: WI
Join Date: Dec 2011 Motorcycle(s): 250R (street), 250R (dirt) Posts: A lot.
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I have cr33's and I love them. But you also know what I did to my motor. |
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June 12th, 2014, 10:07 AM | #9 |
dirty boy
Name: Joe
Location: Johnstown, PA
Join Date: Sep 2012 Motorcycle(s): I don't even know anymore?? Posts: A lot.
MOTM - Apr '14
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could you oval bore a stock carb? How would it work with the throttle valves (or whatever they are) on the exit side since they would still need to seal at idle so you couldn't bore to much off that part of the inner diameter. I guess you could cut new ones and put them in to fit the new inner diameter (hmmm)
I have never futzed with a vacuum carb much so it is kind of new to me. Dirtbike carbs with mechanical slides are so much more simple. I have a spare carb laying around and I just want to play around with it and really want to try to oval bore it out. Should be interesting at least if I don't completely destroy the carb in the process.
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I love the smell of burning pre-mix in the morning I don't think I'm a lot dumber than you thought that I think that I thought I was once. |
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June 12th, 2014, 10:51 AM | #10 | |
ninjette.org sage
Name: bruce
Location: northern illinois
Join Date: Jan 2012 Motorcycle(s): Race bikes:08 Ninja 250,11 R6,16 ZX6,SV650.3 HD-1947,2-2003,2010. 1946 Indian and a lot of dirt bikes.2 Posts: 999
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