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Old March 24th, 2020, 12:59 PM   #1
ssrsupermoto
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2004 Ninja 250 air fuel screw question

I have a 2004 Ninja 250 with 8k miles. Carbs were ultra sonic cleaned and rebuilt using All Balls kit. Set the air fuel screw at 2 turns out. Float height was set wet level with the fuel bowl mating surface of the carb body. Sync'd carbs. New NGK Iridium IX Spark Plugs CR8HIX. Adjusted valves. I feel like there is a "dead" spot at 1/4 -1/2 throttle at constant speeds. I read other forums saying this bike was lean from factory and some recommend 2.5 turns out. Would having the air fuel screw 2.5 turns out help this issue?
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Old March 24th, 2020, 01:40 PM   #2
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Hi Brad and welcome to Ninjette!

Yes, there's a slight lean mid-range that's not there if carbs are factory-fresh clean. Otherwise there's slight hiccup that can be improved with 2.5-3.0 turns out on pilot along with 1-2mm worth of washer-shims under needle heads.
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Old March 24th, 2020, 03:02 PM   #3
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FWIW.....I've had specific issues with All Balls pilot screws differing from stockers in that they seat at different levels of "lightly seated".....therefore 2 turns on stocker is not equivalent to same setting on the aftermarket, thus throwing general "starting points" off from norm.

Experiment on the bench...take a stocker (without spring and oring) install to lightly seated....look in the venturi for the length of metering tip penetration

Do the same with an aftermarket....comparing tip penetration.
I've found varying amounts of penetration....slightly differing heads not allowing full seating equal to stockers...therefore inaccurate as to "number of turns out".

I've opted to clean and use originals over any supplied kit pilot screws, due to many production or vendor variations out there. This on both EX500 and 250 carbs (identical pilot screws)

Wish i had pics (worth 1000 words) Maybe soon.
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Old March 24th, 2020, 03:37 PM   #4
ssrsupermoto
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Did you find out that the All Balls fuel screws were leaner or richer then stock.
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Old March 24th, 2020, 04:26 PM   #5
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MOTM - Nov '18, Mar '17
found a few variations, but generally rich

An alternative...totally disregard the number of turns, opting to find the sweet spot, cleanest idle (usually the highest RPM) for each cylinder, bike fully warmed and running at idle.

As I just posted in another thread...while running, lightly seating a given screw should cause that particular cylinder to drop off...progressively backing it out again should restore the cylinder to running again. Find the sweet spot, each side, adjust idle as required within the process if necessary.

If you lightly seat a pilot screw with no accompanying RPM drop off....something she's a no-good. I'll surmise this may be the case with the aftermarket screws. Let us know how you do.
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Old March 24th, 2020, 05:42 PM   #6
ssrsupermoto
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Well you were 100% correct, swapped out the air fuel screws and even at 2 turns same as when I had the All Balls screws in the OEM air fuel screws make it idle much better. Also added 1mm of shims under the needles, really help that dead spot. Can’t thank you enough.
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Old March 25th, 2020, 07:11 AM   #7
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Quote:
Originally Posted by ssrsupermoto View Post
Well you were 100% correct, swapped out the air fuel screws and even at 2 turns same as when I had the All Balls screws in the OEM air fuel screws make it idle much better. Also added 1mm of shims under the needles, really help that dead spot. Canít thank you enough.
That's pretty common...

(for Gordon)
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Old March 25th, 2020, 07:20 AM   #8
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MOTY - 2018, MOTM - Nov '17
Quote:
Originally Posted by ssrsupermoto View Post
Well you were 100% correct, swapped out the air fuel screws and even at 2 turns same as when I had the All Balls screws in the OEM air fuel screws make it idle much better. Also added 1mm of shims under the needles, really help that dead spot. Canít thank you enough.
Yes, listen to "carb master" !!!
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