Does anyone have these? thoughts? dyno results? etc.....?

Well I can't tell you anything specific that you don't already know. I'm guessing the're not a CV carb so throttle response should be better. Also the larger opening will flow more air if you have accompanying head work etc. So better throttle response more power if jetted right. Only downside is cost. Are you running a non oring chain? Its an easy way to pick up a few horses.

Everyone says the FCR carb on the DRZ400 is basically the best mod you can do to it so it may be worth it on the ninjette. CV carbs kind of suck ass, the FCR should respond to mods better, as well as have much better throttle response.

Yes I have a non oring chain and plenty of mods. My stock carbs are not responding cc well and I will most likely upgrade.

Many people have the cr31's but I want an accelerator pump and the extra flow.

Makes sense. That would probably be a good choice for you then. I wish I could help you more with dyno charts but I haven't found any. I would be interested to see the improvement over stock carbs.

do you mean these??



Sudco Introduces Keihin CR31 Carb Performance Kit for Kawasaki 250 Ninja
Sudco International continues to expand its extensive product line of high performance carburetors kits for street and dirt bikes with this new dual carb Keihin CR31 Kit for the latest 2008-09 model Kawasaki 250cc Ninja street bikes.

The Keihin Special CR is a pure racing carburetor featuring a larger than stock smoothbore venturi for high air flow and precise fuel meeting. This CR Kit provides for increased horsepower, particularly when combined with other engine modifications. This CR twin carb kit will work with the stock Ninja throttle cables and can run with modifications to the Stock Airbox, with separate Clamp-On Filters also available from Sudco, or with the tuned Velocity Stacks provided in the Kit.
Sudco Part No. 016-3205 for the Keihin CR31 250 Ninja

http://www.sudco.com/NewProducts02.html

Those are the ones people usually get. They also offer fcr 35 carbs.

I will try to get a pic and post it.

Mike, I think you know more than me here, but hear me out.


35mm carbs have a larger diameter. This would let in more air, but would it not also lower the intake velocity? Even the ninja 300 (which has 34mm TB's I believe) has a secondary set of butterflies and a taper inside the TB to control intake velocity at small throttle openings. I've followed your build and theory on your engine and I know your engine is sucking in more air (think that's why the 28mm stock carbs are limiting you, not enough air volume in the given time), but would you be better to use the 31's than the 35's to keep the velocity up?

Idk, I'd have to see some math to really give any definite help on 35's vs 31's. Every idea I've got is just speculation.

Mike, I think you know more than me here, but hear me out.


35mm carbs have a larger diameter. This would let in more air, but would it not also lower the intake velocity? Even the ninja 300 (which has 34mm TB's I believe) has a secondary set of butterflies and a taper inside the TB to control intake velocity at small throttle openings. I've followed your build and theory on your engine and I know your engine is sucking in more air (think that's why the 28mm stock carbs are limiting you, not enough air volume in the given time), but would you be better to use the 31's than the 35's to keep the velocity up?

Idk, I'd have to see some math to really give any definite help on 35's vs 31's. Every idea I've got is just speculation.

Very good comment Chon :thumbup:

In one case please let me correct you, the Ninja 300 TB's are 32mm.
With a 35 Carb the driveability in high revs maybe would be possible but I think below 6000/7000 rpm this would not work.

Ah, 32mm. For some reason I had 34mm in my head.

Attached are the pictures of the FCR 35's.

I believe the 35's taper and/or the boots are specially made to taper in as I have been assured that the match/align.

***this is not my bike, but instead the test bike the sudco used***

here are some pics of the cr31's

***this is not my bike, but instead the test bike the sudco used***

Here is my problem: when I slowly open my throttle now the motor coughs/bogs then accelerates. When I hold throttle steady she can studder (jetting lean). She is a b#/&* to start and only accepts choke when it is cool to cold outside...any other time kills it instantly (suggesting too much fuel). At high rpm low throttle situations she is rough getting back on the gas.

Much of this would say jetting if each piece was looked at seperately....however all together I think they point to carbs that cannot handle the motor and its dynamics.

I have gone through them a lot and I even had a trusted tuner go through them.

How did it run with the stock carbs?

that is how it runs with the stock cv carbs.

I am thinking that I need to upgrade. In talking with Racer x, the tunability of these will be MUCH better. I am simply trying to see who, if anyone, has them.

Oh, I thought those pictures where of your bike. I would run the FCR's over the stock CV. Especially with the engine mods. My experience has always been positive when switching away from the CV's.

Not yet. Those are the test bikes that Sudco used and they show that these carbs will fit the stock airbox.

See poll thread:

http://www.ninjette.org/forums/showthread.php?t=149608

I assume no one has these as I have received no answer.