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Old November 30th, 2019, 05:54 PM   #1
Detrailers
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Carb issue

Have a 2007 Ninja 250r that I rescued. Got everything back together, fully cleaned carbs and gas tank. Has a new aftermarket vacuum operated fuel petcock, new plugs and air filter too. I've got one last issue that is driving me mad. I can't get it to idle right. If I twist the idle thumbscrew enough to get it to idle, then the revs dont come down when you blip the throttle. If I turn it down to where the revs come down quicker then it dies and when it does, really hard to restart. Any ideas??
I'm wondering if I pull the caps off the idle screws and bring them out a bit if that will help.
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Old November 30th, 2019, 06:25 PM   #2
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i'd suggest a synch with an accurate, pro manometer, followed by setting each pilot screw to its "sweet spot"....highest RPM with best response done with bike fully warmed.
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Old November 30th, 2019, 08:54 PM   #3
Detrailers
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I just thought of something else too, if the idle screws are still factory sealed, could they still be clogged because I was unable to remove and clean them and this causing idle issues? I soaked both bodies in carb dip but maybe the needle gummed up
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Old November 30th, 2019, 10:04 PM   #4
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If the idle is hanging the carb is out of sync. I would sync first and re adjusting the pilot screw just like Ducatiman mentioned.

If the carb is already out you might want to install a Dynojet kit for an improved idle and less hesitation. It's different for every Ninja, but my 250 would hesitate on idle and at 6500rpm before I did a re-jet. Now it's just smooth all the way.
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Old November 30th, 2019, 10:36 PM   #5
Detrailers
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Well I know what I'll be doing tommorow.. thx everyone
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Old November 30th, 2019, 11:58 PM   #6
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Jet kit not needed unless you’ve got bigger pistons, wild cams and/or full exhaust upgrade. Stock engine and carbs can be tuned optimally by adjusting pilot screws.
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Old December 1st, 2019, 07:38 AM   #7
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Originally Posted by Detrailers View Post
I just thought of something else too, if the idle screws are still factory sealed, could they still be clogged because I was unable to remove and clean them and this causing idle issues? I soaked both bodies in carb dip but maybe the needle gummed up
If pilot screws remain factory sealed, the pilot circuits were never *truly* cleaned within your efforts.

As an '07 is how old now? I'd suggest to have new pilot orings *on hand* before attacking this. Upon disassembly, they are usually found flattened.

My synch and adjustment suggestions still stand as well, just basic tuning reaction to your reported idle fluctuations
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Old December 1st, 2019, 09:38 PM   #8
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Thx for all the input. I drilled out the caps today and adjusted the idle screws after thoroughly cleaning them. I also discovered what I think the culprit is, one cylinders float needle was leaking slightly, so I think what was happening is it would start and idle ok, and then fuel would slowly flood the one side which is what would kill the idle and then be tough to restart..

Since I'm there I'm going one step up to 108 mains and one shim under the needle. Everywhere I read said these bikes were lean and one step up on the needle and MJ helps them quite a bit. Please stop me if this is wrong but every liquid cooled Kawi I've ever worked on has been lean stock.
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Old December 2nd, 2019, 12:20 AM   #9
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Quote:
Originally Posted by Detrailers View Post
Thx for all the input. I drilled out the caps today and adjusted the idle screws after thoroughly cleaning them. I also discovered what I think the culprit is, one cylinders float needle was leaking slightly, so I think what was happening is it would start and idle ok, and then fuel would slowly flood the one side which is what would kill the idle and then be tough to restart..

Since I'm there I'm going one step up to 108 mains and one shim under the needle. Everywhere I read said these bikes were lean and one step up on the needle and MJ helps them quite a bit. Please stop me if this is wrong but every liquid cooled Kawi I've ever worked on has been lean stock.
They usually come lean no doubt. That's why I mentioned every Ninja 250 is different. I though my bike was stock until I did a tune up and found out I had K&N filter with no snorkle pipe and drilled airbox. I went with a jet kit followed the recommended setup, saved a bunch of time on tuning, and never looked back. It ran even better when I replaced the air box and added a slipon w baffle using the same dynojet stage 2 setup.

Shimming the needle should take the idle hesitation, but it doesn't always work. Whats been done to your bike? There's a lot of factors to consider. For example, 108 main jets might not work on a stock bike due to running rich, but it might on full exhaust and high flow filter. Carb tuning takes time, on a fully stock bike maybe just play with the idle mixture. I would also check for vacuum leaks that would definitely affect idle problems. Ive had many vacuum leaks on my bike throughout the years.

Also, are the valves in spec before tuning? I did it on my 08 before and if I remember it was shim under bucket, but your 07 should be easier to work on.
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Old December 2nd, 2019, 11:18 PM   #10
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FIXED! So today I replaced the leaky float needle, put everything back together and it runs great. This along with cleaning and backing out the mix screws, and synching the carbs and it starts and runs smoooooth. Didnt do the 108 mains because the general consensus is it doesn't need it, but I think putting a shim under the needle helped, midrange feels much better.
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Old December 3rd, 2019, 07:41 AM   #11
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...but I think putting a shim under the needle helped, midrange feels much better.
Every case is different, but... I had a shim under each needle and it helped a stumbly midrange that my '05 had. I had it that way for a couple years. Then I had Ducatiman return my carbs to like-new condition and leave out the shims. The engine has never run this well since I bought the bike.
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Old December 3rd, 2019, 12:39 PM   #12
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Quote:
Originally Posted by Detrailers View Post
FIXED! So today I replaced the leaky float needle, put everything back together and it runs great. This along with cleaning and backing out the mix screws, and synching the carbs and it starts and runs smoooooth. Didnt do the 108 mains because the general consensus is it doesn't need it, but I think putting a shim under the needle helped, midrange feels much better.
Good job! Yeah, going to bigger main jets is hail-mary attempt after not being able to properly clean carbs. Which is what most people do and it "works", so problem was factory jets were too small right?

Well, bike ran fine when brand-new leaving showroom floor, with factory-fresh clean carbs. So there's no reason other than clogged carbs that would cause them to not run like factory-fresh bike (assuming valve-adjustment is correct). Main-jets don't affect idle and off-idle behavior much anyway. Most of that idle and off-idle behavior is adjusted by pilot-screws. So after thorough cleaning back to factory-fresh condition (not possible without ultrasonic and micro soda-blasting), you'll just need to ensure carbs are synced and adjust pilot-screws for "best idle" behavior.
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