Haven't Seen Carb Issue Like This

[jeremy_283]

*I SEE THERE IS A BETTER FORUM FOR THIS (sorry), please delete

It is an 07 Ninja and I've complete disassembled, cleaned, used 100+ PSI blasts of air and the issue still exists.

- I saw no holes in the diaphragms
- all vacuum line replaced
- valve clearance is good
- air filter clean
- carb boots tight
- mixture screw 2.5 turns out
- cylinder compression is good

Issue: When cold the bike won't even idle. I hop on while keeping revs up (3-4000 RPMs). Once warm it will idle decently around 1750rpm (indicated on cluster). It will still occasionally die though and be very difficult to restart.

Note: if idling a 1750 and I lightly load the engine enough with no throttle to drop the RPM to say like 1400rpm the idle won't pick back up but it will continually die down unless I twist the throttle.

1750rpm is the lowest RPM I can maintain a reliable idle at

Thoughts?

[jeremy_283]

Completely disassembled, cleaned, used 100+ PSI blasts of air and the issue still exists.

- I saw no holes in the diaphragms
- all vacuum line replaced
- valve clearance is good
- air filter clean
- carb boots tight
- mixture screw 2.5 turns out
- cylinder compression is good
- used wire to poke through some passages and sprayed carb cleaner in others to verify a good stream in others

Issue: When cold the bike won't even idle. I hop on while keeping revs up (3-4000 RPMs). Once warm it will idle decently around 1750rpm (indicated on cluster). It will still occasionally die though and be very difficult to restart.

Note: if idling a 1750 and I lightly load the engine enough with no throttle to drop the RPM to say like 1400rpm the idle won't pick back up but it will continually die down unless I twist the throttle.

1750rpm is the lowest RPM I can maintain a reliable idle at

Thoughts?

[Triple Jim]

I'd say that when you were cleaning, you missed some small idle passages. Air doesn't always do it, it's best to use a brass or copper wire and poke it through all the passages you can find.

[jkv45]

Did you clean the inside of the jets and small holes in the jet holders?

Did you bench-sync the carbs? Did each idle mixture screw have a spring, washer, and o-ring?

Are you sure the gas is fresh?

Read through this section and see if anything may not be assembled or adjusted correctly - http://faq.ninja250.org/wiki/How_do_...n_the_carbs%3F

[jeremy_283]

Originally Posted by jkv45

Did you clean the inside of the jets and small holes in the jet holders?

Did you bench-sync the carbs? Did each idle mixture screw have a spring, washer, and o-ring?

Are you sure the gas is fresh?

Read through this section and see if anything may not be assembled or adjusted correctly - http://faq.ninja250.org/wiki/How_do_...n_the_carbs%3F

Did you clean the inside of the jets and small holes in the jet holders? YES

Did you bench-sync the carbs? Did each idle mixture screw have a spring, washer, and o-ring? YES, VISUAL SYNC. ALREADY APPEARED CORRECT

Are you sure the gas is fresh? YES

I think I am going to pull everything back off and soak it in pine sol for 4 days. Following that I will clean the little passages with copper wire. (maybe carb cleaner?) I don't want to disconnect the fresh rubber hoses cause they are on there TIGHT and carb cleaner may be damaging

When I cleaned it initially the pilot jets were nasty and maybe something worked it's way up into the small little pilot holes on the carb body. Being unable to easily spray from the inside (where the air flows through) of the carb to the exterior maybe some debris is still there and never made its way out since I only really sprayed from outside towards the inside

http://faq.ninja250.org/wiki/Cleaning_the_carbs_2

[Racer x]

Did you replace the pilot jets? That is my knee jerk guess. Sounds like pilot jets are restricted.

[ducatiman]

in this case, consider modern methods... ultrasonic.... may be the hot ticket....working areas otherwise inaccessible

[Triple Jim]

I know you know carbs, Gordon, but I've heard of cases in which extended ultrasonic cleaning didn't get every passage clean, and wires were required. Of course the particular ultrasonic machine, cleaning solution, and technique could affect the results.

[ducatiman]

Wires theoretically great, but truly limited in their ability to access tiny, snake like inner passages, some of which branch off like roots of a tree.

Suggest soda blasting, combinations of chemicals, heat, ultrasonic, compressed air...multiple "courses" as needed. Whatever it takes.

A "driveway carb clean" can't compete with the efficiency of modern equipment.

[csmith12]

Perhaps its... not the carbs. ijs Sorry for starting so simple, but did you spritz around with carb cleaner to check for vac leaks?

[NinjaBraap]

So a few things, first, what year Ninja 250. Second, I'm working on both a 2004 and 2008, which have different pilot screw settings. Standard startup position prior to fine tuning is different for each year. For the 2008 and up, left is 2 1/2 turns out from seated, while the right is 1 3/4 turns out. For 2007 and before, it's 2 turns out from seated on both left and right. I found that especially the 2008 and up tends to be very picky about its factory pilot screw settings for that first startup.

The next thing, as for cleaning as some have already said about your cleaning, use brushes and sonic cleaning for best results. I use high octane clear gas for cleaning, and let all metal parts sit for at least a few days in it after taking literally every piece apart. Another thing though is that rubber parts such as gaskets, o-rings, and diaphragms need replacing. Another possibility is that you'll need to replace the main and slow jets. This brings me to the next point, if you modified the air intake (e.g. high flow filter, high flow air pods/air box delete) then guaranteed you'll need to re-jet and tune accordingly.

In case you need to re-jet, or decide to re-jet the best place by far is JetsRus

Also, that idle is extremely high. Universally for Ninja 250s is 1300+/- 50rpms. Part of this could be due to the fact that you have your pilot screws 2 1/2 turns out on both, and all you need to do is follow the service manual's instructions for proper adjustment. Typically you start at factory settings for your year, start up, let idle and warm up to operating temperature (if you don't know or have a gauge just warm up for 10-15 min, go for a quick ride around the block, or wait for the cooling fan to kick on). Once at operating temp, turn the pilot screw out until your RPM's peak, and/or then start to drop off. Then turn the screw in until again the RPM's peak, and/or then start to drop off. Then set it as close to the middle as possible, and repeat on the other carburetor. Remember to count the number of turns from factory to make it easier to set in the middle. Also, keep in mind that this is an absolute requirement if you modified the air intake or exhaust, but it's just a good idea regardless.


I know that's long, but that's just about everything I've encountered/learned from cleaning and tuning a good number of Ninja 250s, which are one of my favorite bikes. In case you don't have the service manual I've attached screen shots from both the 2004 and the 2008 manuals. 2004 applies to 2007 and before, 2008 applies to 2008 and up until the change to 300s.

2008 and later:


2007 and before (specifically 2004):

[corksil]

Or you have the carb vacuum lines going to the wrong places. It's easy to do and I've done it before.

The 07 and 09/12 carb lines were slightly different and you don't notice in the common pictures online because the fuel inlet hose comes off the back side of the carb in the picture and you can't see it.

[Z1R rider]

I've had the rubber manifold (between carb and head) crack under the clamp where it pushes onto the head making a vacuum leak.

[jeremy_283]

It is a 2007 bike but the carbs are basically the same as 08. I soaked the carbs in pine sol for 4 days. Stripped most everything off of them except for the throttle plate and choke assembly. I also left the plates connecting the two carbs in place since those screws are pretty tight.

Immediately washed carbs and sprayed with WD40 (or the steel will flash rust). I have since rode and washed the bike, even around the carbs, no rust issues.

The bike will now start no problem. It occasionally likes to die down but a light twist of the throttle will keep it from dying. It will idle around 1500RPM though.

I am thinking I should just leave it as is since I got the bike for $250 with 7,000 miles.

The running issue is much better now. It had previously died in traffic and almost didn't want to start back up. The way it runs now I don't think that will happen again. It will also idle no problem when warming up.

[jkv45]

Originally Posted by jeremy_283

The bike will now start no problem. It occasionally likes to die down but a light twist of the throttle will keep it from dying. It will idle around 1500RPM though.

Might just need some fine-tuning.

Checking that the carbs are synced and making fine adjustments to the idle mixture screws may get it running 100%.

Good to hear it rideable now. Good work!

[NinjaBraap]

Sounds like you just need to re-jet it with new stock size jets and fine tune the pilot screw. Also, yes the carbs are pretty much the same as the 2008, I've used pre-gen with 2008 and up before. However because of the power differences in the 2008 and up engine the pilot screw setting differences do still matter. Also, the carburetor body's and float bowl pan are aluminum, not steel. Soaking in a carb cleaner or petrol is a much better solvent than pine sol for cleaning, and you don't necessarily need to spray WD-40 on everything. I live in the PNW near the ocean where it rains a lot, is humid, and has a high salt content (hence chlorine) and have yet to have a single carburetor flash rust, or rust at all with proper care. As long as you dry it out completely and put it right on the bike with fuel running through it asap it'll be just fine.

I'd just drop by JetRus and grab a couple of your size main and slow jets for each carb and through them in, then fine tune the pilot screws. That should even out your idle and restore it back to original function. You can get OEM equivalents for about $5 each, so in total you can fix the issue for $20.

[jeremy_283]

Originally Posted by NinjaBraap

Sounds like you just need to re-jet it with new stock size jets and fine tune the pilot screw. Also, yes the carbs are pretty much the same as the 2008, I've used pre-gen with 2008 and up before. However because of the power differences in the 2008 and up engine the pilot screw setting differences do still matter. Also, the carburetor body's and float bowl pan are aluminum, not steel. Soaking in a carb cleaner or petrol is a much better solvent than pine sol for cleaning, and you don't necessarily need to spray WD-40 on everything. I live in the PNW near the ocean where it rains a lot, is humid, and has a high salt content (hence chlorine) and have yet to have a single carburetor flash rust, or rust at all with proper care. As long as you dry it out completely and put it right on the bike with fuel running through it asap it'll be just fine.

I'd just drop by JetRus and grab a couple of your size main and slow jets for each carb and through them in, then fine tune the pilot screws. That should even out your idle and restore it back to original function. You can get OEM equivalents for about $5 each, so in total you can fix the issue for $20.

The throttle plate that the cables connect to as well as the bridge between the carbs is steel. Carb cleaner is rough on plastics and rubber so that wouldn't have been good for the choke assembly of fuel hose fitting.

One of the pilots although visibly open was not a shiny brass color near the small diameter hole.

My thing was what if there is some sort of corrosion or blockage in the tiny carb body passage ways that I cannot see. I've set the mixture screws 3 turns out, 2.5, and 2. Not much of a difference in running performance so I stuck with 2.5.

[NinjaBraap]

That's why you remove all plastic and rubber parts, you don't want to soak them in anything really, just clean off or replace the plastic parts, and replace all rubber parts, as there can be micro cracks that you can't see. Also as I said before, the starting position is 2 turns out, but you need to fine tune that after starting. It could sit anywhere between seated to almost full out honestly. I'm not here to argue, just give some insight and try to help.

[jeremy_283]

Originally Posted by NinjaBraap

That's why you remove all plastic and rubber parts, you don't want to soak them in anything really, just clean off or replace the plastic parts, and replace all rubber parts, as there can be micro cracks that you can't see. Also as I said before, the starting position is 2 turns out, but you need to fine tune that after starting. It could sit anywhere between seated to almost full out honestly. I'm not here to argue, just give some insight and try to help.

The plastic fuel hose fitting is not a removable part

[ducatiman]

correct, the fuel inlet elbow is NOT serviceable

During a clean, leave it intact.....do not crack it. Actually 2 separate parts.... a pressed brass nipple lies beneath the plastic.
There is no Kawasaki OEM part # for either, though aftermarket one piece elbows are available, requiring a puller device to remove the original and pressing procedure to install the aftermarket replacement in to the body.

The vent rail and fuel rails ARE removable and replaceable, require rack splitting to accomplish. A true refurb includes oring replacement on each.

[ducatiman]

Originally Posted by jeremy_283

I've set the mixture screws 3 turns out, 2.5, and 2. Not much of a difference in running performance so I stuck with 2.5.

i wanted to respond to this....bike warmed at around 1200RPM idle , turning the pilot screw inwards lightly to bottom *should* create a stumble.

As the throttle plates are just about closed, the pilot port is solely supplying fuel...closing the screw creating fuel starvation....resulting in an idle drop.
Progressively opening the screw should then raise the RPM....achieving the position that offers highest RPM and best throttle transition is the "sweet spot"....performing this on each cylinder. Don't rely on "2.5 turns" , just a good starting point to enable setting procedure.

If no reaction from the idle screw ..something is amiss. Unmetered fuel entering the combustion chamber? Pilot fuel or air paths blocked? Combination of ?

[Alex]

/moved to pre-gen tech

[Alex]

/merged