2012 Ninja 250R Bogging/Sputtering On Take Off Running Rich

[dan151]

Originally Posted by Triple Jim

See if you can relate throttle position to the problem areas. Correlation that way is generally much better that trying to relate RPM to them, and it can help to figure out which carb circuit(s) are causing trouble. Sometimes it helps to put tape on the twist-grip and mark 1/8, 1/4, 1/2, etc.

Take off at anything less than 50% throttle results in a bog which recovers most of the time on level ground with slowly increasing throttle input. If on an incline, it will bog down severely and stall out if you take off at less than 50% throttle.

[Bob KellyIII]

Definately sounds like the same problem I was having.... god only knows what changed but it won't run worth a darn..... I had to put 3 shims under the jet needles..... try 2 first and see if the bog goes away I did but I still had a slight bog around 4~5 grand at half throttle....
added the last shim ( a tiny washer) and the problem went away completely!
it is also very important to adjust the airscrews under the carbs you have to get them to fastest idle or it WILL effect the running of the engine up to half throttle ! these are picky carbs !!!!! close isn't good enough with these !
.....
Bob......

[Triple Jim]

Originally Posted by dan151

Take off at anything less than 50% throttle results in a bog which recovers most of the time on level ground with slowly increasing throttle input. If on an incline, it will bog down severely and stall out if you take off at less than 50% throttle.

50% throttle is primarily running on the needles and needle jets, so that would indicate that they are probably not far off ideal. I assume you mean that if you take of with WOT it runs OK too, so I'd look at the off-idle circuit, which is the pilot circuit that's so hard to get truly clean.

I'm used to Mikuni VM carbs though, so maybe others can add to this.

[dan151]

Originally Posted by Bob KellyIII

Definately sounds like the same problem I was having.... god only knows what changed but it won't run worth a darn..... I had to put 3 shims under the jet needles..... try 2 first and see if the bog goes away I did but I still had a slight bog around 4~5 grand at half throttle....
added the last shim ( a tiny washer) and the problem went away completely!
it is also very important to adjust the airscrews under the carbs you have to get them to fastest idle or it WILL effect the running of the engine up to half throttle ! these are picky carbs !!!!! close isn't good enough with these !
.....
Bob......

Just installed two #4 washers on each needle with no improvement to the symptoms. The bike runs noticeable richer than before above 50% throttle which makes sense given the change. The bike ran great overall above 50% throttle before so I don't believe the shims are my solution.

[dan151]

Originally Posted by Triple Jim

50% throttle is primarily running on the needles and needle jets, so that would indicate that they are probably not far off ideal. I assume you mean that if you take of with WOT it runs OK too, so I'd look at the off-idle circuit, which is the pilot circuit that's so hard to get truly clean.

I'm used to Mikuni VM carbs though, so maybe others can add to this.

I agree and yes, if you take off with 50%+ throttle its beyond the problem area so the bike accelerates just fine. Same applies for cruising at 50%+ throttle.

What I don't understand is if the pilot circuit was clogged, wouldn't the bike be running lean due to a fuel restriction?

[Triple Jim]

Originally Posted by dan151

What I don't understand is if the pilot circuit was clogged, wouldn't the bike be running lean due to a fuel restriction?

I'm assuming it is running too lean.

[dan151]

Originally Posted by Triple Jim

I'm assuming it is running too lean.

The bike appears to be running rich under 50% throttle. The plugs are blackened with soot, occasional black soot out of the tailpipe and you can smell the rich mixture in the exhaust fumes.

[Bob KellyIII]

If there was not a change for the better with the shims, then take them out ...that is not the problem....
I agree with Jim that it sounds like the pilot circuit ! if you had the carbs out and all apart you probably removed the airscrews and then set them to what the manual says every time I have done that the bike would not run worth a darn ! the air screws MUST be set to fastest idle on each one before it will run correctly again.... plus if the pilot circuits inside the carb are not truly clean
that is the problem.... the passageways are very hard to clean the photo that helped me the most is this one below. notice how the passageways intersect in 4 directions... ? when you squirt carb cleaner in one hole it should come out all 4 holes but you will only see some out of the restricted ones those are the ones you want to concentrate on.... squirting from every direction with a good carb cleaner that will take out varnish is essential many of the carb cleaners no longer can dissolve varnish ....and I know the manual says don't poke wires into the holes but you have to in order to get them clean I use a spring that I straightened out so it can go around corners if I am very careful.... please understand that if you bust off a wire inside a carb you destroyed the carb because you cannot get it out.... so it is a big risk.... but yet the pilot circuit must be cleaned and cleaned very well they are so small of passage ways that just about any crud in there will restrict the flow of fuel and you'll get a poorly running engine.
.....
Bob
Also check the float level on each carb....

[Bob KellyIII]

I am guessing that you have a stuck float or just adjusted wrong too much fuel would be running rich like you say and it would run really poorly but as the RPM's get high enough it will start using all that excess fuel and clear out and run fine.....
sounds like float level as I was assuming it was a lean condition as well
maybe one of the floats broke or got bent....slip a clear tube on the carbs and bend it up along side the carb and turn the petcock to PRI that should show you the fuel level in the carbs I am guessing the fuel level will be above the bowl seam,(at least on one carb) if so you found the problem....
Bob........

[Triple Jim]

Originally Posted by dan151

The bike appears to be running rich under 50% throttle. The plugs are blackened with soot, occasional black soot out of the tailpipe and you can smell the rich mixture in the exhaust fumes.

OK, no argument there. Seriously over-rich is indeed often one or more sticking floats.

[dan151]

Originally Posted by Bob KellyIII

If there was not a change for the better with the shims, then take them out ...that is not the problem....
I agree with Jim that it sounds like the pilot circuit ! if you had the carbs out and all apart you probably removed the airscrews and then set them to what the manual says every time I have done that the bike would not run worth a darn ! the air screws MUST be set to fastest idle on each one before it will run correctly again.... plus if the pilot circuits inside the carb are not truly clean
that is the problem.... the passageways are very hard to clean the photo that helped me the most is this one below. notice how the passageways intersect in 4 directions... ? when you squirt carb cleaner in one hole it should come out all 4 holes but you will only see some out of the restricted ones those are the ones you want to concentrate on.... squirting from every direction with a good carb cleaner that will take out varnish is essential many of the carb cleaners no longer can dissolve varnish ....and I know the manual says don't poke wires into the holes but you have to in order to get them clean I use a spring that I straightened out so it can go around corners if I am very careful.... please understand that if you bust off a wire inside a carb you destroyed the carb because you cannot get it out.... so it is a big risk.... but yet the pilot circuit must be cleaned and cleaned very well they are so small of passage ways that just about any crud in there will restrict the flow of fuel and you'll get a poorly running engine.
.....
Bob
Also check the float level on each carb....

Mixture screws were reset on a fully warmed engine after each change was made to the carburetors in order to achieve the target idle. 2.75 - 3 turns is usually what it takes to reach target idle.

The carburetors have now been cleaned three times and I visually checked the pilot circuit was clear with carb cleaner and compressed air by visually verifying that fluid was streaming out of the four passages. I'm still not convinced this is the issue as it would result in a lean condition which I am experiencing the opposite.

Everything seems to be pointing to continued issues with the float levels. I will try another level wet test now that the carbs are back on the bike and report back.

[Bob KellyIII]

When checking the fuel level in the float bowls you commonly use a clear plastic tube hooked to the drain at the bottom of the float bowl, then turn the drain screw so fuel runs out the tube.... then you raise the tube along side the carb.... sense the carbs are slightly tilted in instilation you simply devide the width of the carb in half and then place the tube there and that will give you the reading on that carb... personally I would error on the lower side than the upper side when adjusting the fuel level there is about 1/4" of lee-way with fuel level in most carbs.... I do not know how much lee-way you have on these carbs however but I would think within 1/4" you should be good but not above that if the level of fuel is above the seem of the float bowl to the carb they are set too high.... there is an upper limit and the float seam of the bowl is it ...it can't be higher than that personally I would want it about 1/8" less than the bowl seam...
.......
running too rich with stock parts can only be one thing in my book.... floats !
now you could have a sticky float, or a float needle valve that is not seating
or a leaky gasket under the float needle seat (that un screws) which is highly unlikely but stranger things have happened before !
....
it is also possible that with all this crappy running that your spark plugs are now fowled but chances are if they run good at high RPM they are still good..... although that is the way bike spark plugs fail, they crap out under a load but pick it up once your going good..... sense your fighting this you might pull the plugs and clean them real good or just replace them but at $12.00 apiece I would just sprey them real good with carb cleaner and put them back in !
....
Yes even with the #40 pilot jets in my bike I find that 3 turns out is about right for the air screws .
....
hang in there ! I know working on the Ninja is one of the hardest bikes to work on I have ever encountered....there is no room to work on anything on that bike ! and if there IS room you have to take several things off just to get to it ! ...
if you get mad...take a break and chill ....usually (not always )there is a very logical reason it is doing what it is doing..... it has no choice it is mechanical it does only what it can..... it's very rare to have a engine defy logic..... and when it does you will usually find it's the guy turning the wrench that had the wrong idea ! I know this from years of experience..... and I still screw up !
.....
Bob......

[Bob KellyIII]

Don't feel bad the first time I tried to clean the carbs I had to do it 3 times as well before it would run decent..... it still wasn't perfect but it was good enough
but after a winter's setting she was back to her crummy running at low RPMS
so I just sent the carbs to Ducattiman and had him clean them
when I got them back the bike had a huge major flat spot in mid range Ducattiman offered to double check them, so I sent them back to him and he double checked them and assured me they were fine.....
so I was tasked to getting the bike to run right once again it was no easy task
I tried a bunch of different things and finally wound up doing minor modifications ( shims under the needles) and that cured it....
why cleaning the carbs caused that I have no frigging idea I am at a complete loss to explain it.... but it is what it is !
it's not Ducattimans fault ! he did exactly what I wanted the carbs have never looked that good sense I got the bike..... but something changed ! this is one of those cases where I may never know what caused it .
I got through my Ninja's screw-up.... and I am betting you can too just hang in there ! don't give up !
....
Bob.......

[ducatiman]

Originally Posted by Bob KellyIII

now you could have a sticky float, or a float needle valve that is not seating
or a leaky gasket under the float needle seat (that un screws) which is highly unlikely but stranger things have happened before !
Bob......

FALSE INFO
both EX250 and 500 seats are pressed into drillings, no gaskets exist underneath.
We should be so lucky.

[Bob KellyIII]

thank you for pointing that out Gordon ! I was just trying to think of all the flooding problems I have ever ran into in bike carbs.
Bob....

[ducatiman]

Originally Posted by Bob KellyIII

thank you for pointing that out Gordon ! I was just trying to think of all the flooding problems I have ever ran into in bike carbs.
Bob....

in any event, FWIW your comment does not apply at all to EX250 and 500.

[ThatmendoguyYT]

awesome! glad you have figured that issue out, this is my exact same issue, and i have had my carbs out and re cleaned everytime.. 30 times! maybe a few more, i lost count.. but i will give your jetting and float heights a go and hopefully it will be good just like yours... will update eventually, i need to buy some jets and more shims now.. i almost sold the bike but i am VERY glad i seen another forrum.

[Bob KellyIII]

You must understand this is not a straight forward fix for all that ails the bike
you have to play it by ear and discern what the "PROBLEM IS" !
it worked for my bike there is no guarantees it will work for yours !
.... However for some reason the Ninja 250 seems to do this...I have noticed it several times with no real explanation as to the cause.... I still have no idea what caused this to happen.... but I got around it by treating the symptoms
not by finding the cause.... and in 99.9% of the times in mechanics that is a NO-NO you find the cause FIRST .... but in this case there was no cause to find
so,,,,you treat the symptoms and try to get it to run right again....
my bike may still not be perfect because of that fact but I think it's good enough for me to at least ride it now !
....
Bob...

[dan151]

Finally located the problem, found the "needle jets" to be missing from both carburetors. It appears the last owner did in fact disassemble the carburetors for cleaning and failed to reinstall the jets and gave up on the bike when it would not run correctly. As a result, fuel was flowing past the slide needles and through the main jets constantly, causing a very rich running condition. The problem was right in front of me the whole time.

Part #16017 and circled in red on the attached Kawasaki parts fiche. You can see in the attached pictures as well, there should be brass jets sticking up into the throat of the carburetors.

Replaced the missing parts and the bike is now running properly. Thank you to all those members who provided guidance, I very much appreciate your time and patience!

[Bob KellyIII]

WELL DONE ! that part not being in there would have been hard to spot !
those spacers go in in one direction by the way
....
Glad you found the problem ! that would definitely do the problem ! good work finding it ! Now go ride the bike and get to know it.... just be a very cautious rider, cars don't look for bikes half the time !Assume they don't see you and act accordingly.... that method has worked well for me through the decades
....
Bob.....

[DannoXYZ]

Wow, good job!!!

When in doubt about carbs, confirm everything is in bone-stock factory OEM condition way it left factory!

[Bob KellyIII]

Interesting....in the 3 photos above you can plainly see the brass tips of those spacers are not protruding into the throat of the carb like they should be....
.... I bet Danno or Gordon would have cough that if the pic was posted ! their sharp on those things !
.....
but it is surprising how hard something like that is to spot when it's not in there to begin with .... ... when you finally see it it's like, well of course !
....
Well done !
Bob......