2006 250 ninja carb questions

[Cafe Racer]

Ok I picked up a non-running 250 with 7300 miles. It had been sitting for 6 years. Bad main fuse. Ok let's try to start. No choke, shot of ether and gas. Starts right up. Few minutes it settles into a nice 1200 rpm idle. Now let's go for a ride. Shifts well, but under load breaks up at 6000 rpms. Will rev higher no under load 7-8000 rpms. No bog at all.

Took carbs apart and were remarkablely clean. I am sure some of those very small passage ways are blocked.

Question:
My plan is to do the K&N pod filter.
Should I try to get the bike running stock or jump right to the pods? I am good at rebuilding carbs. Plus you guys have great info about jets and shims.
I already removed the air box, but can reinstall.
Is there any stator issues or electrical issues that cause a ninja to break-up at 6000 rpms.

One comment about Bluecollorbobbers. I asked for a discount code and they gave me discount code. I mentioned I was not totally running right. Lance, the owner, suggested I should hold off on buying the kit until I was running 100%.
Hard to believe he would delay a sale because I was not running 100%. Here is a guy who has more concern for a buyer, who he does not know, then making a sale. My hat is off to him and his company.

[spent_too_much]

My opinion, is to get it running correctly - stock, before you change things up. If you don't, you'll never know where the issue resides.

In my opinoin, a bike sitting for that long needs a thorough carb cleaning - Ducatiman style.

[ck.mecha]

You mention you already have the airbox removed, when you were testing was it also removed? If so, that is almost certainly the problem. Put the airbox back on and drive it a couple hundred miles

[empire00]

Originally Posted by ck.mecha

You mention you already have the airbox removed, when you were testing was it also removed? If so, that is almost certainly the problem. Put the airbox back on and drive it a couple hundred miles

THIS ^^^

I spent entirely too long working on a Chinese scooter this year trying to troubleshoot the carb before putting the airbox back on.

[Cafe Racer]

The bike was totally in stock configuration when I did my testing. Air box had not been touched except to make sure the cheap crappy piece of foam was in place.
My biggest issue is the front tire is original to the bike, 2006. It is dry rotted Beyond belief. Not safe under any conditions. I made a trip through the gears. Then ripped it through the gears. It would break-up at 6000 rpms.

I guess my question are there any reasons the bike would break-up at 6000 rpms except for a carb issue. I have lots of experience with other bikes, not Kawaski's. Some bikes have stator issues and other electrical issues that effect certain rpm ranges. What are the issues with little Ninja's?

Has anyone kept the air box and changed out the piece of foam for a K&N filter that goes in the box?

What I hate about the current air box design is it make carb removal a great pain.

[jkv45]

When trying to diagnose carb issues it's easier to pinpoint the problem if you think in terms or throttle opening (1/8, 1/4, 1/2, ...WOT) instead of RPMs.

These bikes don't tend to have electrical issues, so I would concentrate on the carbs.

I would pull the plugs to look at their condition and color.

I would also check the battery voltage, terminal connections, and ground contact to the frame. A battery or connection issue can cause it to run erratically as well.

[empire00]

does it break up at 6k while in neutral setting still?

[Ram Jet]

Originally Posted by Cafe Racer

Ok I picked up a non-running 250 with 7300 miles. It had been sitting for 6 years. Bad main fuse. Ok let's try to start. No choke, shot of ether and gas. Starts right up. Few minutes it settles into a nice 1200 rpm idle. Now let's go for a ride. Shifts well, but under load breaks up at 6000 rpms. Will rev higher no under load 7-8000 rpms. No bog at all.

Took carbs apart and were remarkablely clean. I am sure some of those very small passage ways are blocked.

Question:
My plan is to do the K&N pod filter.
Should I try to get the bike running stock or jump right to the pods? I am good at rebuilding carbs. Plus you guys have great info about jets and shims.
I already removed the air box, but can reinstall.
Is there any stator issues or electrical issues that cause a ninja to break-up at 6000 rpms.

One comment about Bluecollorbobbers. I asked for a discount code and they gave me discount code. I mentioned I was not totally running right. Lance, the owner, suggested I should hold off on buying the kit until I was running 100%.
Hard to believe he would delay a sale because I was not running 100%. Here is a guy who has more concern for a buyer, who he does not know, then making a sale. My hat is off to him and his company.

Think twice about the air box removeal and the K&Ns. I don't believe you will gain 1/2 a horsepower. In fact, my non scientific opinion is you will lose power. If Kawasaki could have produced more horsepower with your modification they could have reduced their unit manufacturing cost and had a quicker motorcycle.

Bill

[Cafe Racer]

I believe what you say. Honda i know put a lot of time into proper design. Pod filters rob HP on CX500. I just hate the air box design. Makes removing carbs a total pain.
Maybe the answer is the air box mod by cutting the battery box off.

Been working on the carbs today. Pretty clean, but the carb cleaner came out yellow. Need to order jets and o-rings.
The main jets are 105. Need to buy a small Screwdriver to remove the slow jets. I will have to look up what the stock size is.
Not having my shop close at hand is a pain. My winter spent in FL is supposed to be riding time. I got bored and bought a bike.

[Ram Jet]

Originally Posted by Cafe Racer

I believe what you say. Honda i know put a lot of time into proper design. Pod filters rob HP on CX500. I just hate the air box design. Makes removing carbs a total pain.
Maybe the answer is the air box mod by cutting the battery box off.

Been working on the carbs today. Pretty clean, but the carb cleaner came out yellow. Need to order jets and o-rings.
The main jets are 105. Need to buy a small Screwdriver to remove the slow jets. I will have to look up what the stock size is.
Not having my shop close at hand is a pain. My winter spent in FL is supposed to be riding time. I got bored and bought a bike.

Thin twice about separating the battery box from the maim air box unit. If you do you'll have to fabricate a support for the rear of the air box. Here's the best way I've found to remove the carbs;

https://www.youtube.com/watch?v=AD5br8HCfn0

The only change I would make the next time mmy carbs are off is to slightly elongate the two bolt holes under the batter to make it easier to attach the carb boot the the carburetor intake bells.

I a 2007 and the only jet change I made was the Main jets and went from a 105 to a 110. No shims. Could I do more? Maybe but I'm very happy with the way she runs now. Stock airbox and Yoshimura mufflers.

Bill

[Alex]

/moved to pre-gen tech

[Cafe Racer]

Thanks Ram Jet.
I guess I will reinstall the air box. Since I will not have any fairings and easy to get to the fender bolts the video makes sense. The only thing I missed was loosing one side of the rubber hose. I finally did get them out the left side. I think I may have said few swear words and had some not to nice things say about the idiot who made it almost non-removal. MC design are a series of compromises. I guess the air box need to be wider then the frame.

No air box frees up lost of room far other stuff.

[Ghostt]

I would highly recommend that you DO NOT REMOVE THE AIR BOX, the carburetors on the bike are CV type and need to box to function properly, buy a K&N that fits the OEM airbox

PreGen K&N KA-2586 Kawasaki High Performance Replacement Air Filter https://www.amazon.com/dp/B000FGI50G..._sp0SxbGTXHE2J

Long boring but important answer, CV carbs stands for "constant velocity". The function of the carbs is dependent on having a calm reservoir (airbox) from which to intake air at said constant velocity. Pods draw from the turbulent, unpredictable air swirling past them as you ride, which is anything but constant. Other carbs work fine with pods. CV's = no bueno, save yourself the headaches.

Now onto jetting, first you need to tune the idle mixture screws first, I recommend 3 full turns out from bottom as a good starting point, then fine tune them afterwards. As far as buying a jet kit, I personally don't have one on either my 250, or 500 ninjas

[Cafe Racer]

Ok heading to the trailer to reinstall the air box. Guys over on the CX500 forum fight this problem all the time.

By the way Gostt asked if it died under no-load. It seemed to rev fine past 8000. I did not get crazy with the throttle.

I have to reinstall the head light and instrument cluster and tach cable, tank and something to sit on. The only things on the bike right now is the wiring harness, engine, forks and wheels.

Oh well.
Thanks,
CB

[DannoXYZ]

Might have leaky slides...

[Ram Jet]

Originally Posted by Cafe Racer

Thanks Ram Jet.
I guess I will reinstall the air box. Since I will not have any fairings and easy to get to the fender bolts the video makes sense. The only thing I missed was loosing one side of the rubber hose. I finally did get them out the left side. I think I may have said few swear words and had some not to nice things say about the idiot who made it almost non-removal. MC design are a series of compromises. I guess the air box need to be wider then the frame.

No air box frees up lost of room far other stuff.

Hey C.R. air box or no air box your little Kaw is going to be just fine. Just to let you know I was just sharing my 69 year old thoughts with you. Half the fun of motorcycling is personalizing your ride. I don't want to sound like some sort self appointed motorcycle oracle.

Get wrenching!

Bill

[Cafe Racer]

OK got the bike put back together enough to test ride. Still need to remount the mufflers.

Ordered a rebuild kit from ducatiman. That guy is on top of his business.

Why order stuff of eBay when we have a guy right here!

[ducatiman]

And I thank you for supporting a fellow forum member rather than a stranger on ebay.

Your stock pilot jet size is 38. A proper size screwdriver is imperative to aid in safe removal....they can be a bear to have to drill and remove, best to avoid that scenario.

If I may suggest....remove the pilot screw (tiny oring, washer and spring) AND the pilot jet.....aggressively spray your carb cleaner and compressed air back and forth between these 2 orifices....which form a major part of the pilot "pathway". Assure that the air correction jets (both main and pilot) are clear as well.

All the above done with both diaphragms SAFELY REMOVED from each body.

Good luck with the cleaning procedure.

[Cafe Racer]

Ducatiman got the parts on to me the same day I sent in the order. Our great USPS seems to have lost the package. They have been saying all week it was on the way from Jacksonville FL to St Augustine, a trip of about 30 minutes.

Anyway I reassembled carbs with the old orings and float valves.

I put enough to stuff back on the bike to test ride. Instruments, seat, mufflers, that stinking air box, and the gauge cluster.

Bike fired right. After a little warmup I hit the street. The bike took off and pulled like hell through 6 gears. I dropped her down a couple of gears and went to 13,000 rpm. No hesitation, no flat spots idled great.

Now tearing it down again for the blue Collor bobber cafe kit.

Thanks for all the advice.
Keep you posted on develops.

[choneofakind]

Originally Posted by Ghostt

Long boring but important answer, CV carbs stands for "constant velocity". The function of the carbs is dependent on having a calm reservoir (airbox) from which to intake air at said constant velocity. Pods draw from the turbulent, unpredictable air swirling past them as you ride, which is anything but constant. Other carbs work fine with pods. CV's = no bueno, save yourself the headaches.

You keep saying this, but respectfully, you're still not 100% right.

CV = constant velocity. That much is right.

What that means is as the pressure differential across the carb increases, the slides open to increase the orifice area and keep constant air speed through the carburetor. (note that as this happens, the flow rate through the carb increases, so technically the fixed-size intake of the air box actually sees an increase in velocity) The throttle only controls the butterflies, but the slides respond to the pressure differential. That's why changing those springs makes such a huge difference in how the engine behaves without much change in the spring rate or preload. Bernoulli stated this relationship between differential pressure and fluid velocity:
https://en.wikipedia.org/wiki/Bernoulli%27s_principle

There's no hard rule anywhere that says CV carbs are incompatible with pod filters, just tribal lore and wives tales. It's well documented that more power is possible with a pod filter on these bikes without affecting ride-ability adversely. Although, anecdotally, I will say a pod filter bike seems to be slightly more affected by weather changes than an air box bike. Also anecdotally, if the tuner has some concept of how each component works, tuning for a pod filter is no different than tuning for an air box. Read through threads where people had issues with pod filters; more often than not, it's because they had no idea what they were doing with jetting when they started.

You are right though, when it comes to tuning for consistency, any intake will benefit from consistent airflow patterns. Consistency is always the name of the game for tuning and testing. But also remember the pregen air box is from the days when the design goal of an air box was purely to filter the incoming air; unlike today where an air box is designed to flow and swirl in just the right way to help atomize fuel and fill the cylinder perfectly for 0.001% more efficient burn.

[Ram Jet]

Originally Posted by choneofakind

You keep saying this, but respectfully, you're still not 100% right.

CV = constant velocity. That much is right.

What that means is as the pressure differential across the carb increases, the slides open to increase the orifice area and keep constant air speed through the carburetor. (note that as this happens, the flow rate through the carb increases, so technically the fixed-size intake of the air box actually sees an increase in velocity) The throttle only controls the butterflies, but the slides respond to the pressure differential. That's why changing those springs makes such a huge difference in how the engine behaves without much change in the spring rate or preload. Bernoulli stated this relationship between differential pressure and fluid velocity:
https://en.wikipedia.org/wiki/Bernoulli%27s_principle

There's no hard rule anywhere that says CV carbs are incompatible with pod filters, just tribal lore and wives tales. It's well documented that more power is possible with a pod filter on these bikes without affecting ride-ability adversely. Although, anecdotally, I will say a pod filter bike seems to be slightly more affected by weather changes than an air box bike. Also anecdotally, if the tuner has some concept of how each component works, tuning for a pod filter is no different than tuning for an air box. Read through threads where people had issues with pod filters; more often than not, it's because they had no idea what they were doing with jetting when they started.

You are right though, when it comes to tuning for consistency, any intake will benefit from consistent airflow patterns. Consistency is always the name of the game for tuning and testing. But also remember the pregen air box is from the days when the design goal of an air box was purely to filter the incoming air; unlike today where an air box is designed to flow and swirl in just the right way to help atomize fuel and fill the cylinder perfectly for 0.001% more efficient burn.

The airbox also effectively rids the crankcase of harmful, contaminated crankcase gases and provides a relatively cool supply of fresh air to the carbs. And unlike K&N filters actually provides a source of clean air to your carburetors. UNI filters are a different story.

Bill

[Cafe Racer]

I got my carb parts from ducatiman. I really like the bolt set. No more wrong sized Philips head screwdriver.
He even included a little piece of vacuum line I needed.

Thanks,
Soon to be a ninja 250 rider.

[Ceeloo Yello]

Have fun with your BCB cafe kit.

[Dab]

Originally Posted by Ram Jet

The airbox also effectively rids the crankcase of harmful, contaminated crankcase gases and provides a relatively cool supply of fresh air to the carbs. And unlike K&N filters actually provides a source of clean air to your carburetors. UNI filters are a different story.

Bill

crankcase gases can also be vented out through a separate "air filter" to allow gases out and keep particulants from entering.

[Ram Jet]

Originally Posted by Dab

crankcase gases can also be vented out through a separate "air filter" to allow gases out and keep particulants from entering.

Vented but not DRAWN/EVACUATED out of the crankcase.

Bill

[DannoXYZ]

Originally Posted by Ram Jet

Vented but not DRAWN/EVACUATED out of the crankcase.

Bill

There's an additional benefit of connecting crankcase to airbox, more POWAH!!! Yes, been documented and dyno-tested ad-nauseum that having some vacuum in the crankcase creates less drag for the crank and pistons to move around. Up to +10% more power in some tests.

So how do you create this vacuum in crankcase? Attach hose from crankcase to intake! Of course you'd need some kind of sealed container to generate the vacuum... a box perhaps?

[Triple Jim]

The had better not be much vacuum in the airbox, or WOT flow will be severely restricted.

[DannoXYZ]

Sure there is some restriction between filter and butterflies. But vacuum levels aren't as great in airbox than between butterflies and intake-valves. Most restriction is in intake-ports. So mods done before intake-ports don't have much effect (as been reported by most people having done so). Porting intakes is best bang-for-buck/effort upgrade. Or just bolt on a 300 head.

[Z1R rider]

The real purpose of the crank vent going to the airbox is for emissions, runs the blow-by gases back into the combustion chamber to be burned instead of just venting to the atmosphere.