More carb questions?

[xXecuterXx2]

This Ninja i have is outfitted with a muzzy exhaust system, and It hasn't been rejetted, any idea/recommendations as to what setup would be ideal?

[jkv45]

How does it run now? Are the idle mixture screws accessible?

If it runs decent now, I would start by fine-tuning the low and midrange. Typically, the idle mixture is set lean, so going to a setting of 2 1/2 turns out gets you better idle and transition to midrange. If you make a significant adjustment you will most likely need to move the idle speed back down to the correct setting of 1300 RPMs after making the mixture adjustment.

The needles are usually also on the lean side, and adding shims to lift them slightly gives you better throttle response and acceleration in the 50% throttle range.

If it pulls cleanly and strongly through the midrange (50% throttle opening) and continues to pull strongly into the WOT range the main jet is pretty close. Know that when you roll the throttle wide-open it takes time for the slides to lift, so you need to be full-throttle for a few seconds before you are actually "wide-open" and can determine if the main jet is the proper size.

Stumbling, stuttering, or falling flat as you get into the main jet will tell you you need to make adjustments. Most often, too rich will give you a stumble/stutter/popping and too lean will give you a flat/bog/hesitation.

You can also look at your spark plugs to give you some indication of your overall mixture. Optimum is a light tan color.

[dino74]

Jetting is also affected by airbox mods. Are you running a stock airbox?

[xXecuterXx2]

When I'm below about 6k there is a stutter, like jerkiness, but when i get higher she's butter on biscuits, and i am running stock airbox

[Racer x]

2.5 turns on idle screws . Balance the carbs from there
40 pilot
110 main
0990 air filter ,at least till your jetting is sorted.
Maybe 108 mains
Go one hotter on the plugs

Ride see how it does

[Ghostt]

Keep OEM airbox, go get a K&N tune pilot screws per the write-up below,

Your initial setting should be 3 full turns out from the bottom, remember just slightly tighten them, don't go all Conan on them.



Then warm it up, slowly turn 1 side pilot screw in until the rpms drop, then back out till RPM's peak (and no further)* Twist throttle...see how it reacts...tweak to taste.
Repeat on other side... test ride. You're looking for best throttle response and transition from just cracked to 1/4 throttle opening or so.*

Thats a quickie, 10 cent tutorial on setting pilot screws.**

As far as balancing goes, don't touch the synchronise setting using the vacuum method, if you must, do it this way,

You can sync with the carbs in hand. Back the idle adjustment off to close that carb then match the second carb to it with the sync screw. You can then turn the idle adjustment up while using a thin feeler gauge (maybe .002") between the throttle plate and the throttle bore, adjust to just fit, and then check the second one and adjust to match. If you have good feel for this it will run fine once installed.

It would do folks well to take a minute to review and understand what a sync tool does, how it works. And take another minute to look at the carb linkage and sync adjustments available to fix irregularities that might occur. It can help take some of the mystery out of this as well as stop unnecessary carb sync screwups.

Meaning, that the carbs were right once, the butterflies were matched and it performed well, but then changed. Undecided And the problem somehow occurred in the butterfly direct shafts, or the sync screw turned or wore that pad that it rests on, or the carburetor pairing/ bridging brackets twisted in relation to each other, and enough so that the butterflies no longer operated in sync, such that performance noticeably suffered. And a fix will be accomplished by changing the butterfly position, the only thing the sync adjustment does. Hmmm. Really? Undecided

Meanwhile, the tool measures vacuum at each individual runner. That's all it does, how it works. And vacuum is effected by a huge list of things, butterfly position being only one of them, and the only one addressed with that tool while turning those sync screws. The rest of that list includes, valve adjustment, jetting, float level, compression differences between cylinders caused by wear as well as factory CC differences in the head, intake runner, as well as flow by port variations, etc. Variations in cams, wear or factory tolerance. Then there's the potential big one, pilot jets and pilot screw mixture settings. All of those effect the vacuum and will be read by the sync tool, accurately identifyng the difference that exists, and with the only adjustment being used to "correct" the problem, move the butterfly relationship, one to the next.

It's that clear understanding that has me of the opinion and long time practice to not touch the sync screws on a set of carbs that were right once and were never dismantled from the rack. And jet cleaning as well as float needle changing doesn't require that they be dismantled. And further, if I DID dismantle a set of carbs, I just matched the butterflies on the bench at assembly, using a feeler gauge, and then never touched them again, never gave them another thought.

That method, properly executed, will have THAT portion of the complete equation, balanced flow to each cylinder in a multi-cylinder/ carb application due to butterfly position, satisfied entirely adequately. And in fact, it has worked for me every time I've done it on every bike (as well as individual runner/ butterfly V-8 intakes, all eight) that I've ever owned or any that I've fixed for others. And the times I fixed for others was usually after an attempt by others to sync the carbs, chasing a problem, or sometimes not even chasing a problem, but one they created wth a sync tool, chasing a problem from that list, that was never a butterfly position change problem. Those linkages are so direct and simple that they don't know how to screw themselves up. Not enough to care about.

I'm sure this will start a lot of controversy so I won't argue it, just offering it for those who understand the whole picture that I outlined and might make good use of it. It is what I've done, on every engine I ever worked on, including blue printed racing engines as well as regular old, high mileage street stuff. I've had at least four, four cylinder bikes with over 100,000 miles that ran quite well, the whole time, and never had a carb sync performed. When they did finally get a total disassembly, this is how I set them up, on the bench. Over the years I've straightened out at least a half dozen messed up ones, probably more, and on the bench, after fixing the original problem which was fouled pilot jets.

I only posted this because it seems like its coming up fairly often, especially with problems from a sync gone bad. One I would suggest was never a sync problem to begin with. A big or sudden change in performance is NEVER a sync problem. NEVER. Remember that. Cool If there is a problem, and you connect the gauges? YES, there will definitely be an imbalance indicated. But because that hole has a problem that is from the rest of the list. A bad plug, a plugged pilot jet, a screwed up float, a bad valve or setting, etc. Every one of them effecting the vacuum in the intake but NOT from a sudden move of a butterfly position, a sync adjustment.

Why to keep the OEM airbox,

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(K&N KA-2508 Kawasaki High Performance Replacement Air Filter by K&N Amazon.com: K&N KA-2508 Kawasaki High Performance Replacement Air Filter: Automotive Amazon.com: K&N KA-2508 Kawasaki High Performance Replacement Air Filter: Automotive ) that's the short version.

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. I did shim the main needles with a small washer. If needed go up one size on the main jets, maybe.

Is it a full Muzzy system, or just a slip on?

Jetting is a hit and miss unless you have access to an exhaust gas analyzer.

[xXecuterXx2]

Not sure, its got the 2 in 1 header on it. if that matters. i got the bike used so I'm not so sure of everything
Sidenote, oil puddles under the bike when left for a couple hours, nothing major. open to solutions though.

[Ghostt]

Originally Posted by xXecuterXx2

Not sure, its got the 2 in 1 header on it. if that matters. i got the bike used so I'm not so sure of everything
Sidenote, oil puddles under the bike when left for a couple hours, nothing major. open to solutions though.

Full muzzy system then.

[xXecuterXx2]

Ok, thanks for the info bro

[jkv45]

Originally Posted by xXecuterXx2

Not sure, its got the 2 in 1 header on it. if that matters. i got the bike used so I'm not so sure of everything
Sidenote, oil puddles under the bike when left for a couple hours, nothing major. open to solutions though.

Try to locate where the oil is coming from. It could be coming from the airbox, which isn't uncommon. You do need to keep track of the oil level with the Ninja, as it will lose some oil through the crankcase breather (into the airbox).

As far as carb adjustments go, you need to think in terms of throttle opening - not RPM. You can be at 9,000 RPMs and 1/4 throttle or 4,000 RPMs and full throttle. The carb is operating on completely different circuits, and the RPMs are not the deciding factor.

To cure what you are experiencing, do what I suggested in my previous post concerning idle mixture adjustment and needle shims.

[Ghostt]

I agree with Jay, just follow the guides above, and then see if a jet kit is needed, the washers under the main needles is a cheap and easy modification, less than $1.00 for 4 = 4mm washers

[blink.]

Originally Posted by Ghostt

I agree with Jay, just follow the guides above, and then see if a jet kit is needed, the washers under the main needles is a cheap and easy modification, less than $1.00 for 4 = 4mm washers

Where is the best place to get the washers?

[Ghostt]

Originally Posted by blink.

Where is the best place to get the washers?

I picked mine up at my local Ace Hardware, I even got the stainless steel ones

The size needed is 4mm.

[xXecuterXx2]

Sorry for the bump, but my issues persist, i took it for its first ride above 45mph today. While riding i noticed if i hold the throttle still, the bike'll jerk a little, like uneven throttle response or something, I'm gonna make this my main vehicle, so i gotta get her running fine. also, how would i get under the carbs to adjust the screws while its running? i can't seem to fit anything I also only noticed this higher up in the rev range, also, as previously stated, i have a muzzy full system if that point to anything. Need all the help i can get, thanks guys.

[Ghostt]

Adjusting the idle mixture only effects the throttle position to about 1/4 open,

If you look at this write-up, http://faq.ninja250.org/wiki/How_do_...dle_mixture%3F pay attention to the bottom of it, they have some ideas about tools to fit.

Another thing to check is the chain adjustment, if too much slack, it will cause the feeling of surging sometimes.

If your in need of carburetor services PM @ducatiman

[xXecuterXx2]

ok, thanks Ghostt, does he give tips for free?

[Ghostt]

Depends, PM him you also could be in need of jetting, and/or shimming the needles.

Here's some more information about the subject,
http://faq.ninja250.org/wiki/How_to_...roper_main_jet.

http://faq.ninja250.org/wiki/Intake

http://faq.ninja250.org/wiki/Why_wou..._my_jetting%3F

But if you don't access to a exhaust gas analyzer then it's just a guessing game, fortunately the modifications that have been done to the bike I'd fairly common, so someone has the proper information about the jetting.

[jkv45]

Originally Posted by xXecuterXx2

Sorry for the bump, but my issues persist, i took it for its first ride above 45mph today. While riding i noticed if i hold the throttle still, the bike'll jerk a little, like uneven throttle response or something, I'm gonna make this my main vehicle, so i gotta get her running fine. also, how would i get under the carbs to adjust the screws while its running? i can't seem to fit anything I also only noticed this higher up in the rev range, also, as previously stated, i have a muzzy full system if that point to anything. Need all the help i can get, thanks guys.

Where are the idle mixture screws set?

Did you shim the needles?

What main jet are you running? Do you have pod filters?

Isolating the issue will depend on the throttle position where it occurs - is it 1/4, 1/2, 3/4?

Surging and flattening-out is typical of a lean condition, but a stumble/stutter or popping usually indicates rich. Chances are it's lean if you haven't shimmed the needles.

[xXecuterXx2]

Originally Posted by jkv45

Where are the idle mixture screws set?

Did you shim the needles?

What main jet are you running? Do you have pod filters?

Isolating the issue will depend on the throttle position where it occurs - is it 1/4, 1/2, 3/4?

Surging and flattening-out is typical of a lean condition, but a stumble/stutter or popping usually indicates rich. Chances are it's lean if you haven't shimmed the needles.

When i shift in the higher rev range (8+ rpms) i get popping from the exhaust and i definitely get that stumble and stutter, I'm gonna try to open the air fuel screws and see if i get a change, i hope do, i really need this bike to work. and most of the stuttering is in the 1/2+ ranges, and sometimes lower.

[jkv45]

Originally Posted by xXecuterXx2

When i shift in the higher rev range (8+ rpms) i get popping from the exhaust and i definitely get that stumble and stutter, I'm gonna try to open the air fuel screws and see if i get a change, i hope do, i really need this bike to work. and most of the stuttering is in the 1/2+ ranges, and sometimes lower.

Is this while you are wide-open? If so, it would mean the Main Jet is incorrect.

The Idle Mixture Adjustment won't help in that range. It's only controlling the mixture during idle and slightly above.

When you are experiencing what appears to be carb problems, think in terms of the throttle opening and not RPMs.

We need more info.

Are you using pod filters? What Main Jet is in it now? What are the mixture screws set at now? Have you shimmed the needles? Are you sure the fuel is good? What fuel do you run?

[xXecuterXx2]

i've never been wide open, mostly near 3/4 and thats where it is

Stock Airbox

Stock Main Jet

2.5 turns

fresh fuel

91oct from bp up the street
(i know i know, no benefits, i feel like there is, probably the placebo effect to jack a poor teens money)

[xXecuterXx2]

Could i take off the dual inlet plate on the airbow to increase air flow? that seems like it would help if I'm running rich....

[jkv45]

Originally Posted by xXecuterXx2

Could i take off the dual inlet plate on the airbow to increase air flow? that seems like it would help if I'm running rich....

With the stock Main Jet and a Muzzys pipe I wouldn't expect you to be running rich, but you could take the snorkel off and go for a ride. If it's worse you are lean, if it's better you are rich.

You really need to know how it's running wide-open to make a decision on what needs to be done, but for starters i would search around to find what others have settled on for a Main Jet with your set-up.

Have you shimmed the needles?

Run regular 87 - no ethanol if you can get it. Changing from gas with ethanol to gas without ethanol will make a bike with carbs run richer.

[xXecuterXx2]

Ok, ill try that, and no needle shims, i thought that'll run richer, and i figured that could be my issue, but i just got grounded ( i know **** me right?) so ill get back to you in a couple days

[InvisiBill]

http://factorypro.com/tech/tech_tuni...m_engines.html is a good guide for the basics of carb tuning. It'll show you which parts control fueling in which ranges, and what order to tune them in (so you're not going in circles changing things after you change other things).

[xXecuterXx2]

Ok, update time, i yanked the snorkel, and she still runs rich, i got in a couple full throttle runs and pulled the plugs afterwards (hot as hell, watch your fingers) and found they were wet and black, also, she smells like a ATV, so I'm sure of its richness, how do i make it run leaner?? new jets i suppose??? where do i even find jets??

[jkv45]

Originally Posted by xXecuterXx2

Ok, update time, i yanked the snorkel, and she still runs rich, i got in a couple full throttle runs and pulled the plugs afterwards (hot as hell, watch your fingers) and found they were wet and black, also, she smells like a ATV, so I'm sure of its richness, how do i make it run leaner?? new jets i suppose??? where do i even find jets??

There's a problem with the carb or carbs then. Stock main jet with a Muzzy pipe should be leaner than stock - not richer.

You need to pull the carbs and go through them carefully.

Is it smoking? Does it use any oil? Is the airbox oily?

Something isn't right, and I don't think it's the jetting.

[ducatiman]

Originally Posted by xXecuterXx2

Not sure, its got the 2 in 1 header on it. if that matters. i got the bike used so I'm not so sure of everything

New to you...until carb internals are examined and jetting is established, anything is possible. If the PO put on the pipe, possible he "jetted" it too. Very common for folks to grossly overfuel in the search for power.

Main and pilot jets should be marked with numbers. Stock needles are non-adjustable, kit needles use e-clips.

Starting point...establish *precisely* what jetting is in the carbs, how far and where it deviates from stock settings. I'd also advise checking the fuel levels as well, make sure the float needles are, in fact, sealing. While you've got them out, confirm the pilot passages are clear....are the orings dried out?...Check slide action...etc etc etc.

Always good to have carb "consumables" on hand before pulling carbs of unknown origin.
Kits containing orings, float valves, etc. Eliminates downtime waiting for parts.

[xXecuterXx2]

Well ducatiman, I've seen your work, and will say its tempting, so lemme ask you this, could you jet my carbs for me? and maybe a cleaning, PM with prices

[ducatiman]

pm sent

[gokartmozart]

I will soon be tearing down my carbs for ultrasonic soak (been sitting for about 5 years) , Who would be the "go to" person for info and advice ? Also will need a good source for carb parts & gaskets.

[Ghostt]

PM @ducatiman