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Old September 2nd, 2018, 01:14 PM   #1
Iotobe
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Troubleshooting a lean running Ninja

Hello Ninjettes! I recently purchased a 2007 ninja 250 from a seller on Craigslist (who happened to be a friend of my brother). He was made out to be very trustworthy, so I bought the bike (at a good price too).

I came to find that it has some problems (like most old bikes). He made some questionable modifications as well. The bike runs lean and takes ages to warm up and stalls at every stop for the first 10 min of riding. When I blip the throttle the prms hang for a while too. When I use the choke, it revs way up to 8k. The first thing I did was clean the carbs and jets, but it still ran lean. I also adjusted the fuel/air mixture screws which helped a bit. I checked the air box and found that he made a modification to it. He replaced the stock filter with one of those drop in K&N filters that clap the the intake holes on the clamp. My guess is he didn't know to rejet it and that's the root of the problem? I just bought new stock replacement parts for it. Am I on the right track? Does anyone else have any thoughts on what could be making it run like this? Thanks in advance!!
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Old September 2nd, 2018, 05:18 PM   #2
Triple Jim
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You'll find out if the stock filter helps soon enough, and we can go from there.

Your idle mixture is adjustable if you open up the covers over the screws. But it's fairly likely your carbs aren't truly clean, from your description of the problems.

Welcome to the forum, Ian!
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Old September 2nd, 2018, 07:22 PM   #3
DannoXYZ
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Hi and Welcome!

Hey, I used to live right next to Glen Annie Golf Club in Goleta while at university! Then moved downtown S.B. after graduation!

Your carbs are not "clean"! As in factory-fresh clean. Bike ran perfectly fine when it left factory in brand-new condition, and there's no reason it shouldn't if carbs are as clean as they were when leaving factory. Fact that bike doesn't run as brand-new shows that carbs are not "factory-clean". Here's some related threads that will help you.

This post summaries it: https://www.ninjette.org/forums/show...10&postcount=8
https://www.ninjette.org/forums/showthread.php?t=323452
https://www.ninjette.org/forums/showthread.php?t=322846
https://www.ninjette.org/forums/showthread.php?t=321223
https://www.ninjette.org/forums/showthread.php?t=315193
https://www.ninjette.org/forums/showthread.php?t=317977

Also search for "carb refurb ducatiman". Years ago, I spent 2-months, over 40-hrs trying to clean my 2003 pregen carbs with spray cleaners, poking it with various size wires, ultrasonic cleaner for weeks on end. It behaved exactly same as yours. Compared to 2nd 2002 pregen I had which ran perfectly. It started with minimal choke, warmed up within 30-sec, pulled strongly under partial or full-throttle from 2000rpms+ and positively screamed to 14k-rpm readline.

As troubleshooting step, I swapped carbs from better-behaved 2002 pregen to troublesome 2003. It ran perfectly and I realized my "carb-cleaning" was insufficient. Only difference was carbs and my attempts at cleaning the 2003 bike was not restoring it to factory-clean fresh condition.

After searching on here, I sent troublesome 2003 carbs to ducatiman for real refurb job, even got new seals, bolts and hoses along with thorough internal cleaning of all jets and fuel-passages. Put refurbed carbs back on 2003 bike and it ran perfectly like brand-new bike!!!

Since then, I've acquired toxic cleaners for ultrasonic machine along with high-pressure soda-blasting equipment. Even then, yearly carb-cleaning on my 2008 race-bike is not something I look forward to. It takes good 30-hrs to do properly and I don't enjoy it one bit. If you didn't floss out all fuel passages, along with ultrasonic agitation in chlorinated cleaners followed by high-pressure soda-blasting, your carbs are not factory-clean. Therefore, are not behaving as brand-new factory-fresh machine off showroom floor. There IS a way to achieve that level of performance...

Last futzed with by DannoXYZ; September 3rd, 2018 at 10:13 AM.
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Old September 3rd, 2018, 10:06 AM   #4
ducatiman
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thanks for kind words, @DannoXYZ

i'm down to about 5 hours in 1 "session" to do twin Keihin carbs

In the house now a set of badly mauled '98 750RR ninja 4 bangers. I have parts on order to complete the repair work needed. EVERY float bowl screw over tightened to the point of stripping, someone trying to compensate for flattened, leaky float bowl gaskets , rather than replacing the inexpensive gaskets!
Same for diaphragm cover hardware, tightened to the max. An associated corner of a carb body is cracked! Repairs ongoing. A genuine gorilla has made his presence known.

Been awhile since on here, catching up some.
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Old September 3rd, 2018, 11:04 AM   #5
DannoXYZ
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Good to have you back, hope things are going well.

Here's some threads with before & after pictures of ducatiman's work. If your carbs aren't running right, he'll refurb them to brand-new condition. Your bike will run like it just rolled off showroom floor!

https://www.ninjette.org/forums/showthread.php?t=239678
https://www.ninjette.org/forums/showthread.php?t=226815
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Old September 8th, 2018, 07:15 AM   #6
Iotobe
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Wow those pictures are amazing. I'll definitely have to rely on Gordan for peice of mind.

I pulled the carbs out again to attempt another cleaning and one of the pilot jets is totally stripped (I didn't pull it out the first time. Totally new to this). The other one I was able to remove and it had chunks of hair stuck in it. So I think that's the problem. Does anybody know what pilot jets fit these keihin carbs? On jetsrus.com there are about a billion different sizes and shapes. It looks the most like the N424-25B, but I'm not sure...

The air filter hasn't arrived yet. But I'll be glad to return the bike closer to stock anyway. I prefer a quieter ride.

Thanks for the detailed help DannoXYZ! I actually live right by there. I'm a UCSB student myself as a matter of fact.
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Old September 8th, 2018, 10:11 AM   #7
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Yes, stock configuration is simplest and most reliable.
You can find jets for pre-gen Ninja here:
http://jetsrus.com/a_jet_kit_street/...1988-2007.html

To free up stuck jets, i usually use an ammonia solution (floor cleaner) to dissolve corrosion. Then PB-Blaster. A light tap with hammer-driven impact-screwdriver really works well and prevents stripping jet. Not sure why these are made from soft brass, seems like copper-beryllium would be better.
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Old September 8th, 2018, 01:17 PM   #8
ducatiman
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stock size is #38

Stripped pilot jet removal can be a difficult process, very tricky walking the tightrope between careful damage prevention yet aggressive to get the job done. Damaging the pilot threads or the orifice is an no-no.

No doubt, the offending jet will need to be drilled, using a tiny eze-out, you may get lucky OR it'll require piece by piece extraction. Its a nerve wracking job, been there many a time.

I am at your service. Coincidentally, I have #38 pilots in stock here.

If you are apprehensive or lack tools, as carb repair is new to you, and this is a genuinely tricky job, you may choose to send them onward.

My email ducatiman900ss@gmail.com[/email] if need be, I'm at your service.

In any event, good luck going forward with the repair.
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Last futzed with by ducatiman; September 8th, 2018 at 02:39 PM.
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