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Louie, Technician
Category: Motorcycle
Satisfied Customers: 11944
Experience:  25+ yrs. experience
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08 Kawasaki Ninja 250r Cleaned carbs but motorcycle will not

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08 Kawasaki Ninja 250rCleaned carbs but motorcycle will not start. Can pray carb cleaner through breather while cranking and engine will fire, but will not run on its own. Plenty of fuel in carb bowls.

Hi and welcome to the site, I’m Louie. Sorry you had to wait awhile but I’ll do my best to help.

Initially, let's try check and review the basics. Proposed preliminary tries (if have not been done):

  • ensure that the air box + filter is correctly installed with no possibility of an air leak;
  • or for test purposes, instead of "...pray carb cleaner through breather..." temporarily cover the "breather" with the palm of your hand or even a rag when attempting to start.


  • replace tank contents with fresh fuel;
  • check the burn color of the spark plug tips.
Customer: replied 3 months ago.
Here is all that I have done. Cleaned tank, fresh gas, checked pet cock and fuel flow. I've removed airbox and cover with hand while cranking. It gets good suction. New spark plugs and checked to ensure proper gap. Both are getting spark. Both carb bowls are getting fuel from the tank, but it doesn't seem to be getting from the bowl to the cylinders. I have removed and cleaned all primary and secondary jets, air mixture set screws, checked for breaks in hoses.. All of which look good.

Appreciate the post back.

On "...removed airbox...cover with hand while cranking. It gets good suction...", did your palm got wet with fuel?

Customer: replied 3 months ago.
No Sir. I did not. Also no gas smell from the exhaust either. The bike sat for 2.5 years as well.

I understand Tim.

Considering that "...Plenty of fuel in carb bowls..." yet palm was dry when covering the carb mouth, then the contents of the bowl are not rising, It would be indicative still of a carb issue.

When the carbs was cleaned, did you all soak the metal parts into carb cleaner solution?

Checked all the jets? ...ensure all small holes are not clogged? ...used carb cleaning brush similar to the product shown HERE?

Customer: replied 3 months ago.
I did everything but soak in a solution. Used carb cleaner and brushes (like the one you suggested) and ensured all jets were cleaned and all passageways allowed the cleaner to flow freely.

Please click HERE.

Bear with me and re-check/re-clean # 12, the pilot jet and where it is screwed into the carb body.

Additionally, adjust/turn # 13 to 1¾ out from fully seated.

Customer: replied 3 months ago.
Sir... I will re-clean/recheck as soon as I get home from work this evening. I will update you after I have completed and tested. Thanks Louie.

...and would look forward to the update when able.

Customer: replied 3 months ago.
Alright Louie,
I did everything you recommended. Reached and cleaned 12 and 13 and set mixture screw to 1 3/4 turns out from fully seated. Still no change. ��

IF #12 is surely clean, then it would be the very small hole of the carb body itself that may be clogged.

Please consider (re-) soaking all the metal parts overnight or even longer.

Customer: replied 3 months ago.
Ok... I'll pick up a soaker kit and do as you have instructed. I will let you know here in a day or two after I have completed the process and tested. Thanks for your help thus far.

I understand and when able...

Customer: replied 3 months ago.
Hi Louie,
Any chance you can tell me how to remove the fuel inlet tube pictured? It's the only NONMETALLIC part left on the assembly.

Hello Tim,

Either a small screw (least likely) or it is force-fit (most likely). Consider soaking with this fuel inlet tube on top and the cleaning fluid level just enough to have the metal parts submerged.

Customer: replied 3 months ago.
I soaked the carbs overnight and reassembled. I did the same with my atv carb as it's a Kawasaki as well and that thing fired right up and runs great, but the bike is still having the exact same issue. All hoses checked out too. :(
Customer: replied 3 months ago.
Also, as I hold my hands over the carbs and crank there is fuel shooting out. My have does get yet.

With these carbs full cleaned, install the air box + filter and ensure correct/snug fit with no air leak.

Customer: replied 3 months ago.
Instead of the airbox is as a K&N pod filter number KN-0990. That should be sufficient correct?

I would beg to disagree; this model/type would tend to allow more air entry and results to a very lean mix (spark plug whitish) hence would call for a rejetting to compensate.

If running stock jets/carbs, then please use stock air box + filter.

Or consider changing the jets.

Or a workaround if not for test purposes, slip an extra outer layer of generic air filter foam over the pod filter.

While test tuning, I used old woolen socks 1 over the other.

Also, bear with me for likely delays as I would be mobile later playing husband and father.

Customer: replied 3 months ago.
I understand your reasoning. Shouldn't the bike at least start when you place your hand over the breather.Also, understand being a family man myself.

Still a no even when starting considering lower RPM during cranking thus lower vacuum = lower suction to gas intake hence with pod type air filter, the vacuum is further lessened = poorer starting suction.

Customer: replied 3 months ago.
the airbox is fully installed, see included picture, and there is still the same issue. It doesn't even attempt to start. Full choke and I never even hits a lick.

Appreciate your patience/understanding.

For test purposes and as posted above, add an extra outer layer of generic air filter foam over the original air filter inside the airbox. It may even take 2 or 3 layers.

The objective is to reduce volume of air intake to make the mix just slightly rich.

Then test start. If still a no-go, attempt to re-start working the throttle as if trying to flood the engine. Then remove the spark plugs and see if these got wet with fuel.

Customer: replied 3 months ago.
Ok I will do as you have recommended. will let you know as I am in Texas for a work conference.

Yes please when conveniently able.

Customer: replied 3 months ago.
Done as you have said... still a no go. Took out plugs and the arewet and smell like fuel.
Customer: replied 3 months ago.
Sorry should have read they arent wet, but smell a little like fuel. Could it be some kind of vacuum issue not pulling it into the cylinders?

Sorry but I would beg to differ based on the earlier description of "...cover with hand while cranking. It gets good suction..."

Rather than an engine/vacuum issue, it would more point back to the carbs.

Please click HERE. There are two (2) pin holes on the carb yellow tunnel; blue and red (air & fuel respectively). These are responsible for the idling and start up air/fuel mix to be fed to the engine.

When #s 12 & 13 were removed for cleaning, did passing a thin stiff wire where 12 & 13 were resulted to the end of the cleaning wire to appear through the yellow tunnel?

Customer: replied 3 months ago.
Almost certain the were clear but i only shot carb cleaner through passages after soaking. Thinking I may repull them and resoak again. Look at the included pick. Is this all I need do the rebuild kit? Can't seem to find one with the other parts.

These parts are necessary for replacing below parts IF and only IF:

  • float valve # 8 the carb is over filling / flooding; and/or
  • pilot air screw #13 can no longer be adjusted and/or the pin end is deformed.

And as posted before.....Checked all the jets? ...ensure all small holes are not clogged? ...used carb cleaning brush similar to the product shown HERE?


passing a thin stiff wire where 12 & 13 ... resulted to the end of the cleaning wire to appear through the yellow tunnel

Louie and 2 other Motorcycle Specialists are ready to help you
Customer: replied 3 months ago.
Finally got the thing running. Got a jet kit for it and soaked again for over 48 hours! Glad to be done with it. Lol. Thanks for all your help.

Great! Good to hear that the issue has been resolved, congratulations.

Good luck and thank you too for the opportunity to share the information.