Idle Problems of a Biking Noob

[Sampi]

Hey guys, I'm pretty new to motorcycles and ninjas overall but I've been having a great time with my recently acquired 03 250.

I have been slowly going through all the basic stuff needed to be done to used bikes to make sure everything is up to snuff and working properly like filters tires brake lines pads chain etc etc. Eventually when I got through it all I was still having problems with the bike. The ninja will start up pretty consistently usually wanting just a slight bit of throttle to get going. From there it gets finicky. Usually at full choke the bike will idle at or above 5.5k, I've heard thats kind of high and that you should aim for about 2k while warming the bike up I usually try to ease off the choke to bring the idle down. I'll get maybe halfway off the choke and land at about 3k or so before the bike falls out of the choke and dies. Moving past that when the bike passes the cold section on the thermostat it still acts cold and will die unless i have the choke on or baby the rpm with the throttle. Finally when the thermostat is pretty much vertical, about past halfway closer to hot the bike will finally settle into an idle.

The problem now is that that idle is really only stable between 2-3k more often then not on the 3k side of things. This being arizona and all that gets the bike very close to hot very often. Usually I'll let the bike idle high every now and then playing with the idle knob to try and keep the bike from exploding at stop lights. The weird part though is that even the high idles can be unstable. When I'm coming to a stop after downshifting through the gears the bike will tend to die when I pull in the clutch. The only way I've been able to combat this is to baby the throttle while braking and try to "set" the rpm down where it wants to be. If I don't do this and let the engine fall farther than a few hundred rpm down to its 2 or 3k level it falls past and dies unless i catch it again with more throttle.

After some looking around I figured the problem is probably something to do with the carbs and maybe the idle mixture so i pulled them and went through everything with seafoam spray. Power wise the bike ran much better but I was still having the same problems. I've checked through all the fuel and exaust lines I could, I have an inline filter in the mail, and I've been playing with the idle mixture screws for about two weeks now with no real success. Only thing I could find of note is that the air box has a K&N filter in it instead of those standard sheet of foam looking oem things.

Honestly I'm completely at a loss. I have other problems on the bike I can work on in the mean time like replacing the fork seals and such but I really don't know where to go from here even with all the research I've done. Hopefully you guys will have an idea on whats up with this bike and can help me get it running a little better.

Thanks in advance for your time guys


EDIT: Suddenly realizing im in the wrong section and I cant find a way to move or delete this thread...

[Alex]

/moved to pre-gen tech area

[Sampi]

Thanks Alex

[Desmoluci]

Are you sure your pilot jets are clean, with no blockage? I would pull the carbs back off and remove the jets to make sure, they're tiny little passages that get clogged easily. Most poor low speed carburetion problems are related directly to the pilot jets and the associated passageways.

[rubber side down]

sounds like a monster vacuum leak or like has been said idle jet issues and it is running on the intermediate circuit.

[Sampi]

Ive heard vacuum leak once or twice around the web with this issue, is there a way I can go about confirming that that might be the issue?

Regarding the pilot jets, I took the carbs completely apart and made sure all the jets were clean with seafoarm and a small bit of wire (taking care not to damage the jets)

[rubber side down]

while its running spray carb cleaner (or anything that is highly combustible) around the boots that connect the carbs to the airbox and the boots that connect to the engine. Also any vacuum hoses that on the carbs. if it is a leak and you spray some on a leak, normally it will pick up speed because your adding more fuel to the over abundant amount of air it is getting.

[Sampi]

Alrighty, I'll give that a shot tomorrow when I can get my hands on some more carb cleaner

would wd-40 work as well?

[alex.s]

sounds like probably combination of still partially clogged idle jets and maybe a leak in a diaphram? or maybe something in your intake snorkel. cracked vacuum lines sound likely too. i would use something that evaporates cleanly to check with, not wd40.

[Sampi]

alrighty, carb cleaner it is then

hmmm... sadly I've had all of those apart and in my hands already... Most of the lines on the bike have looked pretty good so far, flexible and no visible distress on them. I took the pilot jets and main jets apart and made sure there was nothing visible in them, carefully ran wire through them and made sure I could get a good stream of spray carb cleaner through as well. I guess there are one or two lines that look questionable and though I didnt see anything that looked out of place on the diaphragms I'm not sure how to tell if there is a leak there or not.

I guess if nothing on the outside of the carbs checks out then I'll pull them again when I take the forks off.

[Ninjinsky]

1 Have you checked the carb balancing with a pair of vacuum gauges?
The screw that links the carbs is a tempting twiddle for previous owners and without having the carbs off to measure the butterfly gaps with a gauge (small drill bit shaft) a pair of dials is the only way.
2 These are one of the worst bikes I have owned to get a good slow idle you need to get the balance spot on.
3 Any time beyond a month standing ie long enough for the float bowls to evaporate off will fuzz the carbs and necessitate a strip
4 And fit a fuel filter the idle circuit will use any excuse to clog even a little tank rust
5 Check the filler cap seals (including the little one under the key flap) are clean and moving well otherwise water in the tank is highly likely.

[greenaero]

It sounds like pilot jet problems , as said above the holes are tiny and easily clogged. It has to be clear or the bike can be unrideable .

[Desmoluci]

Originally Posted by Sampi

would wd-40 work as well?

It will, but it slows the engine instead of speeding it up.

[Sampi]

Little update for you guys

I still have work to do with my new can of seafoam to check for vacuum leaks but I got my inline filter in and while replacing my fuel line to accommodate the filter I found that the fuel line was clogged with some sort of rock or plastic like material. I got my new line and filter on and took the bike out for a quick spin. Looks like this made quite a difference because everything is acting differently now. I'll have to do some more rides to find out what exactly is going on now and whether it is still problematic or simply the settings are super off to compensate for the clogged fuel line.

Anyways I'll keep you guys updated as things move along