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Old April 27th, 2020, 02:21 PM   #1
DJohn93
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2007 Ninja 250 - Possible Carburetor Issue?

Hello everyone,

Long time lurker, but new member here. I recently purchased my 2nd bike a few weeks ago, a 2007 Ninja 250 with very low miles. Originally the bike wasn't running at all. I have cleaned out the carbs and the pilot/main jets, drained the gas tank, replaced most of the fluids, and changed the air filter. The bike is now running, but will idle between 3-4k rpm. It will accelerate perfectly fine at this range, but I know its not good to have the bike idle this high. I have adjusted the idle screw for it to idle at about 2k and the bike wants to bog down and slowly accelerate even when fully opening the throttle. If I have it at idling at 1k-1.5k and give it some throttle, it will die. I have looked pretty much everywhere for some help with this issue. Everything I can find seems to point towards the carbs, but they were almost spotless besides the main jets (which have been cleaned now). The only other thing I haven't done to the bike is replace the spark plugs, but I don't think that will help my issue any.

Any assistance would be greatly appreciated.

Last futzed with by DJohn93; April 27th, 2020 at 02:24 PM. Reason: missing words
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Old April 27th, 2020, 05:48 PM   #2
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the '07 has evidently sat dormant a good portion of its life. in sitting, the fuel "drops out", turning into a varnish...obstructing and finally clogging to varying degree and constricts fuel and/or air flow...some,all or none...to get through their tiny, winding passageways.

After some years a "carb clean" is called for, areas where varnish has accumulated must be cleared. Some of those areas are visible, some are not.
Full, complete disassembly is called for to allow full access to these affected areas which include the starter , pilot, air circuits, main mixing chamber, decel circuits, fuel flow pathways. Renewing all pilot, vent and fuel rail orings (at 13 years old they demand replacement) and float valves. Reassembling after aggressive cleaning methods (which vary upon composition of the component involved) following with correct synch, pilot screw and float adjustments (aka setup). Wet testing insures no leaks and correct fuel levels....better to find and correct errors on the bench prior to install on the bike....insuring getting it right the 1st time... no further carb pulls necessary and a reliable runner upon install.

Well, thats what you've got to accomplish here. I left a lot out, too. Examples such as troubleshooting the internals ...inspecting/measuring pilot jets to assure they have not been altered, correcting any assembly errors/missing/wrong parts/poor adjustments, defects or other repair attempts from prior owners...a lot involved in *true* comprehensive carb servicing. Some stuff to consider.
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Old April 28th, 2020, 05:57 AM   #3
DJohn93
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Thanks a bunch for the reply Gordon. I will tackle this in the next few days and be more aggressive with taking it apart. When I originally cleaned out the carbs, I just did the jets and the bowls. Everything else seemed to be in great condition. The bike hasn't even been broken in yet (a little over 2k miles) so I wasn't sure if it was just the carbs or if it could have been something deeper.
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Old April 28th, 2020, 12:20 PM   #4
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Something Gordon didn't address (from your original post):

When you discover a low-miles bike that (years ago) got pushed to the back of a garage and forgotten there's a reason why this happened. Something that would be great to find out when you take possession of the bike.

Sometimes there was nothing wrong with the bike to cause it to be relegated to the darkness. It could be that the owner got a bad scare out on the road and quit riding. Or the bike could have been purchased for a spouse (who really didn't want to ride in the first place).

But if it wasn't something like that, you can assume that there was something wrong with the bike mechanically that the owner couldn't solve. Also, the fact that the owner didn't just go ahead and sell the bike off suggests that he knew something was wrong with it that would interfere with selling it.

Your description of the bike as "very low miles" suggests that the bike got parked well before any long-term carb maintenance issues would normally surface.

If it turns out that your planned re-cleaning of the carbs doesn't help the high-RPM idle problem you might want to investigate the possibility of a vacuum air leak between one of the rubber boots that connect the carbs to the engine's cylinder head.
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Old April 28th, 2020, 12:26 PM   #5
DJohn93
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Thanks Greg. I'll have to check out for leaks. I didn't even think of that as a possibility. Since it seems to be running rich I just assumed it was something to do with the carbs. I purchased it from a friend at work that bought it brand new in 2007. He rode it a couple hundred miles every summer for a few years and said he quit riding it in 2014 after having a kid. So its been sitting for a good 6 years now.
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Old April 28th, 2020, 01:12 PM   #6
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Quote:
Originally Posted by DJohn93 View Post
Thanks Greg. I'll have to check out for leaks. I didn't even think of that as a possibility. Since it seems to be running rich I just assumed it was something to do with the carbs. I purchased it from a friend at work that bought it brand new in 2007. He rode it a couple hundred miles every summer for a few years and said he quit riding it in 2014 after having a kid. So its been sitting for a good 6 years now.
That sounds promising, could be a very solid bike you have there.

You say it seems to be running rich, this is pretty easy to determine: the exhaust either smells strongly of unburned fuel or it doesn't.
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Old April 28th, 2020, 01:15 PM   #7
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Quote:
Originally Posted by greg737 View Post
That sounds promising, could be a very solid bike you have there.

You say it seems to be running rich, this is pretty easy to determine: the exhaust either smells strongly of unburned fuel or it doesn't.
Yes, it smells strongly of unburned gasoline behind the bike.
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Old April 28th, 2020, 03:03 PM   #8
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If that ain't rich (or blatantly leaking fuel) I don't know what is
So this is still occurring after your carb efforts then?

The universal, standard selling point...."it ran when it was put away". As such, buying a non runner off the open market can include risky discoveries....some cheap and easy fixes, some not.

You are fortunate in knowing the previous owner and the history of the bike.
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