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Bob KellyIII · January 4th, 2022, 10:52 PM

the air screw for the adjustment of the fuel ratio at idle only effects the engine up to about 2000 RPM the main Jets effect the engine from mid range to WOT
the throttle valve cutaway is what effects the engine just off idle to just above mid range.
hardly anyone ever changes the throttle valve cut away and most people have no trouble with just off idle because of that (grin)
the ninja has a different set up than the old Mulkini's and they call the parts by different names but the function is the same
too lean a setting in the air screw will make it want to hang at a higher RPM
open the air screw to 2 1/2 turns on the left carburetor and 1 3/4 turns on the right.... I just read the manual and it said to do that ! their not set the same !
you have to get it to idle before you can tinker with the carb settings like synchronization.... if the throttles open at the same time by eye that is close enough for now ! on my Triumph I put a finger on one slide in the throat of the carb and look at the slide on the other and that way You can get them perfectly in unison.... the Ninja has butterflys that actuate the vacume diaphram behind it and that pulls up on the slide so a finger on one butterfly
and looking at the other you can get them in unison fairly easily
....I would try all the way out to 3 turns on the air screws but no further
with it running at 3,000 RPM right now your not running on the air screws anyway so you have to get the RPM down to see if the air screw turning is changing how it is running if you can set the idle to 1500RPM and keep it running that should help you set the airscrews (1000 rpm WOULD BE BETTER !)
i found it super simple to set the airscrews on the ninja with all the fairings off it... on one side but the other side was next to impossible for me ( after market air screw was very tight )so I had to make a tool but I got it running really good just by listening to the RPM at idle and turning the airscrew till it was the fastest.... then back off about 1/8 turn....( leave it a bit rich !)
....
if you have the stock jets you should have put them in the carbs already but if you didn't you should now ! LOL
having too big of main jets will mess you up when your trying to isolate problems.....
too big of main jets do not make it go faster , if their done right they will help
but usually it just runs fat and blubbers on acceleration,and smokes !
the reason to change main jet size is not because you changed the exhaust pipe.... but because the spark plug color check you did after the pipe was put on tells you that the engine is now running too lean. there is a world of difference !
....
"Return it to stock and see what you got" still holds true even today !
when you start modifying things you can get some really strange reactions out of an engine !
.....
later !
Bob....

January 4th, 2022, 10:52 PM	#107
Bob KellyIII Retired motorcycle Mc. Name: Robert Location: Weed, California. Join Date: Jul 2021 Motorcycle(s): 2012 Kawasaki Ninja 250R, 2021 CSC TT250, 1977 Triumph Bonneville 750cc,2001 Honda XR650L. Posts: A lot.	the air screw for the adjustment of the fuel ratio at idle only effects the engine up to about 2000 RPM the main Jets effect the engine from mid range to WOT the throttle valve cutaway is what effects the engine just off idle to just above mid range. hardly anyone ever changes the throttle valve cut away and most people have no trouble with just off idle because of that (grin) the ninja has a different set up than the old Mulkini's and they call the parts by different names but the function is the same too lean a setting in the air screw will make it want to hang at a higher RPM open the air screw to 2 1/2 turns on the left carburetor and 1 3/4 turns on the right.... I just read the manual and it said to do that ! their not set the same ! you have to get it to idle before you can tinker with the carb settings like synchronization.... if the throttles open at the same time by eye that is close enough for now ! on my Triumph I put a finger on one slide in the throat of the carb and look at the slide on the other and that way You can get them perfectly in unison.... the Ninja has butterflys that actuate the vacume diaphram behind it and that pulls up on the slide so a finger on one butterfly and looking at the other you can get them in unison fairly easily ....I would try all the way out to 3 turns on the air screws but no further with it running at 3,000 RPM right now your not running on the air screws anyway so you have to get the RPM down to see if the air screw turning is changing how it is running if you can set the idle to 1500RPM and keep it running that should help you set the airscrews (1000 rpm WOULD BE BETTER !) i found it super simple to set the airscrews on the ninja with all the fairings off it... on one side but the other side was next to impossible for me ( after market air screw was very tight )so I had to make a tool but I got it running really good just by listening to the RPM at idle and turning the airscrew till it was the fastest.... then back off about 1/8 turn....( leave it a bit rich !) .... if you have the stock jets you should have put them in the carbs already but if you didn't you should now ! LOL having too big of main jets will mess you up when your trying to isolate problems..... too big of main jets do not make it go faster , if their done right they will help but usually it just runs fat and blubbers on acceleration,and smokes ! the reason to change main jet size is not because you changed the exhaust pipe.... but because the spark plug color check you did after the pipe was put on tells you that the engine is now running too lean. there is a world of difference ! .... "Return it to stock and see what you got" still holds true even today ! when you start modifying things you can get some really strange reactions out of an engine ! ..... later ! Bob.... __________________________________________________ Its too late when you've gone too far !