2012 250R carb issues

[rockinredhead17]

First of all I would like to thank everyone who is taking the time out to read this post. i'm currently on my fiances account hoping to get some info on the issue her bike is having i do have a mechanical background but have not dabbled much with carbs. i would also like to say that i have done numorous hours of reading and i just cant get my head around this issue.

okay so the bike is a 2012 ninja 250r with just over 1800km she bought it used and we are under the assumption that the 1000km service/ valve adjustment was done the bike does have some tasteful mods done to it including a yoshimura slip on (no intake mods everythings oem)....so late last year the bike started to run very poor at idle didnt matter if i was cold or hot, sitting or going down the road in first gear the idle was spiratic up and down 200-300 rpm acted like it wasnt getting enough fuel you would try to rev it and it would bog...so i pulled the fairings off the bike to access the spark plugs and carbs. I pulled the plugs and the right one was white so a lean condition/ left was a tan (good) i replaced both plugs as a set making sure to check the gap and to torque them as to not distort the ground electrode so i then pulled the carbs togeather with a manual in hand its a 2008 copy and everything was as it should be.I then pulled the bowls off the carbs one and a time to make certain that the parts would not get mixed up left to right finding that the caps were still in the fuel/air screw adjustment to me indicating that they have never been touched (i removed the caps with the method on the fourm)the carbs were clean as a whistle with the exception that the right carb was partially blocked where the pilot jet screws into there wasnt an even spray comming from the top side when spraying carb cleaner though the jet (after a few sprays it cleared right up) i also made sure that when pulling the air/fuel screw i didnt mix up the order of the washer and o-ring i didnt bend the float and also i didnt pull apart the top sides of the carb okay so it was noted at time of removal the pilot screws were L:1 5/8 R: 2 1/8 in the manual it states L: 2 1/2 R:1 3/4 .......personally i never though it idled smooth and to low 1000rpm when you tried to ajust the idle it would get worse when the manual states 1300+/-50rpm . so i assembled the carbs let the bike get nice and hot fan come on a few times then adjusted the idle and it had a lean condition and the idle would hang rpm would hang up after a shot of throttle it would sit at 2500 for about 2-3 sec so i set the carbs to the original settings and it got rich condition where the idle would drop below the base idle after some throttle

so after another few hours of reading i came across a post

http://www.ninjette.org/forums/showthread.php?t=10246

Adjusting the idle mixture screws:
Like any carburetor tuning it should be done with the bike warmed up! With the fairings off just go for a quick jaunt around the neighborhood. Make sure that afterwards if you touch the side of the block it really hurts! That's a good way to figure if it's warmed up. The way I found to get you into the ballpark is to (one carburetor at a time) tighten down the idle mixture screw. Again the M.O.S. with a flat-blade bit in the end fits perrrrfectly to the idle mixture screw. Start tightening the screw down until you can hear the engine idle suddenly drop. Then back the screw OUT 1/4 of a turn or so until the idle is restored. That is your "base" so-to-say.

Now blip the throttle. Nothing crazy, just rev it to 2,500 RPM or so and let go of the throttle. Does the throttle immediately drop to idle?

If not:

If the throttle hangs - The idle circuit is still too lean. Loosen the screw down a little more

If the throttle drops below idle and takes a moment to return - The idle circuit is too rich. Tighten the screw a little bit.

Then repeat the process until the idle is restored damn near instantly after you blip the throttle. I try to err on the side of 'rich' as this will help the bike warm up a little quicker and isn't going to REALLY affect fuel economy or anything in the end.

Repeat for the other side's carburetor. Once you're satisfied with it take it out for a quick ride to make sure things are O-tay!

Like any tuning practice don't make huge jumps in the adjustments. It's really easy especially with 4-cylinder bikes to go nutty turning screws until you don't have a leg to stand on. If you think it's perfect from the get-go, make a mental note at the position of the bit on the idle mixture screw and see if you can mess the idle up and then fix it. If it's back where you had it before, then you truly had it right from the get-go! If you find in the end the bike is stumbling off the line then go back to the drawing board and fiddle some more!

when i do this to the left carb it acts like in should and if i turn it in enough it will kill the bike...but with the right one it makes no differance where i place this screw nothing changed at all ?

sorry for the long post im just trying to give as much detail as possible

[Motofool]

Originally Posted by rockinredhead17

First of all I would like to thanks everone who is taking the time out to read this post..........when i do this to the left carb it acts like in should and if i turn it in enough it will kill the bike...but with the right one it makes no differance where i place this screw nothing changed at all ?

You are welcome, Stephanie's fiance.

This sentence indicates that either the right fuel passages of the idle circuit are still clogged or that too much air is leaking in upstream the jets.

I wouldn't assume that the valves were serviced, unless you know otherwise,

[DaBlue1]

I see where you said, "..the bike does have some tasteful mods done to it including a yoshimura slip on (no intake mods everythings oem)"
"....also i didnt pull apart the top sides of the carb."

Was the air filter clean? Did the snorkel have any obstructions?

The Yoshi slip-on runs better when it is shimmed or the Dynojet Kit 2193 is installed. Unless the previous owner told you there were no intake mods, you probably would not be able to tell without looking. Normally the snorkel gets removed with the Dynojet kit.

The lack of shimming may be a small contributor to the slightly leaner than normal condition as indicated by your plugs, but not necessarily. It is possible to see a grayish-white tip and be normal.
From the NGK website



How to Read Your Spark Plug
FAQ Reading Spark Plugs

You can set the pilot screws at 2.5 turns out each to help even out the idle issue. However you will want to make sure the pilot circuit is really clean as well.

Here is some more info to help with your carb issue.

How Constant Velocity Carburetors Work
http://www.motorcycleproject.com/mot...bs_work_v3.swf

Motorcycle Carburetor Theory 101
http://www.motorcyclecarbs.com/carbs101.pdf

Pipe Jetting (A Must Read)
http://www.motorcycleproject.com/mot...s-jetting.html

Carburetor Jet Tech
http://www.motorcycleproject.com/mot...et_tech_v3.swf