So before I could make a "New ninja 250 owner!" post to say hi, I dropped the bike(used) and ran into a little trouble. The drop was when backing it out of the shed and the gas tank hit the side of the door opening which put some nasty dents in the gas tank. I ran the bike for 10 minutes after that and everything seemed fine mechanicaly. A buddy of mine is going to try and pop the dents back out (the paint is fine) so I removed the gas tank to show him the dents. He needs time before he can work on the dents so I put the tank back on, put some gas in it to ride it some more. At first the bike wouldn't start, the starter and all electronics were fine but it seemed the bike was not getting fuel. After many unsuccessful attempts to start the bike (adjusting idle and choke) it finaly got going with the tanksettoreserve. After a while of of unstable idle in reserve mode, the bike started to iron out and run smoothly, while still on reserve. Now, switching to on, it seems I have the same problem as before with reserve. The bike would go to about 4.5k rpm when the choke was on and when I would make the slightest adjustment to close the choke the bike would lose all rpm and stall. After 10 more minutes messing with the choke and idle adjustment I got it to run for about 5 minutes with the fuel tank "on" before it decided to drop idle rpm to under 1k and stall. I had to pack it away at this point, and I'm going to try to get it to run smoothly again today but if anyone has experienced this before or can notice what might be wrong or what I should check, I'd appreciate it.

I'll try to post a picture of the dents,though I don't believe they are causing the problem with the stalling.



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Dang! Sorry to hear about your mishap. Did it run fine before dropping it?

A few things to think about are:
[ol][*]The choke is touchy no matter what. If you try choking it WHILE the bike is already running, you'll likely kill it unless you engage it really slowly. It's better to choke it before starting.[*]Rolling on and off the throttle while starting is a good way to flood the engine, making it start very hard.[*]If you ever starve it of gas, it'll take a lot of engine cranking to gas back into the carbs. (This has to do with the tank petcock valve and engine vacuum.)[*]If the engine can't run without choke, you probably have a vacuum or air leak somewhere. Check your vacuum lines and carburettor boot clamps. (Or, the idle set **** just isn't set correctly.)[*]Since it didn't start until you switched the tank to reserve, are you just low on gas?
[/ol]Hopefully this will give you a few ideas on what to look for.

Welcome to KF.

 

the gas pitcoch has two tubes that go inside the tank with little screens on the ends of the tubes. maybe one of theses screens is clogged.

 

I was going to say something similar. I bet one of the tuber might of gotten damaged in the fall.

 

Have you messed with your idle adjust screw at all? IT might be that to. And yea if you run it out of gas put the choke full on and the bike will start right back up (trust me i did it to many times lol)

 

Thanks for the advice guys, I'll look into all the suggested checks that I haven't performed already. Starting with the gas lines into the carb (right? I'mnot a gearhead by any means lol). I checked the petcock (off/on/reserve thing right?)and it looked unharmed unless the dent bendsthe screen in the tankwhen it's attached, I did notice that it was at least sending gas into the tube (the tank end was full of gas) but haven't check the carb end to see if there is anything blocking it from going in the carb, I'll check that tomorrow. I'm suspecting the carb. since I noticed the reserve tube runs to a different location on the carb. than the main gas flow tube. Can anyone suggest any checks for this or the suction of the gas line?

The bike ran perfectly before I dropped it and I'm pretty sure I ran it after I dropped it (but before I took the gas tank off) and I'm pretty sure it ran fine then too which leads me to believe I did something to cause the unstable gas supply, maybe dirt got in somewhere...

Some side notes:
I have only used the choke prior to starting the engine.
Bike ran great until I removed the gas tank, emptied it, placed it back on the bike.
I used new highest localoctane gas when replacing the tank.
I can see plenty of gas in the tank, so it shouldn't simply be low.

More detailed +++UPDATE+++

Now when I start the bike, I put the choke on, start it, rpms go high (5k) right away, I back the choke off very slightly and it loses all rpm to a stall.

Seems at idle, w/ petcock set to on, the rpm's fluctuate anywhere between 1kand 2k before it stalls.

When idle is most unstable, hitting the throttle the engine will react well to increase rpm but when I let go, it floats down after a slight pause.

I have had to balance the idle adjust screw (once warmed up)with fairly wide ranges trying to keep idle around 1.3k rpm before becomes more stable, in which it eventually stalls.

Thanks so much for the suggestions guys, it's greatly appreciated!

 

Heres some things to think about. In no particular order.

You have to have the bike warm before deciding on how bad it runs, however it should start with choke and with some adjusting of the choke you should be able to get it to idle around 3k hopefully less. Ride it a bit until its warm shut off the choke and adjust the idle.

Did you set the tank down on the ground i.e. dirt? If so you may have collected some dirt in the openings of the petcock which in turn have made their way into the carbs.

Dont use premium fuel, high octane is misleading to those who dont understand what its actual purpose it. Its for engines that run so hot they predetonate the gas before its supposed to. High performance engines are designed to take advantage of this, also older cars with carbon deposits will knock (predetonation) because the carbon causes the gas to ignite prematurely high octane reduces the predetonation. It actually burns less efficient in engines that arent designed to use it.

The main reason not to use premium fuel especially when gas prices are high is that its old, the storagetank is less full because they order less gas,which can allow moisture to collect, which in the littleNinja is a big deal and will cause horrible running issues.You could have water in the gas in your tank.

You could have knocked crap loose in the tank which have made it to your carbs. I noticed when I painted mine that the paint under the cap flakes that could have gotten in your tank as well. Is it rusty?

As far as dropping the tank, it is possible you bent the tank enough to have smashed the intake. You can use a dental mirror (autozone) and a flashlight to see in the tank or just remove the petcock. You will need to be very careful that you dont create a spark and you will likely need to drain the tank anyway. Also if it runs fine on reserve and crap on the normal setting then you probaby have bent it.
If thats the case buying another usedtank may be cheaper than a new petcock, you may be able to find either on ebay.

If it were me I would first drain the float bowls and let the bike sit overnight on the centerstand. Drain a cup or 2 off the reserve of the tank, this is to try and remove any water that settles to the bottom of the tank, it is vacuum operated so without vacuum applied to the right nipple of the petcock no gas should flow from the tank. I use a shop vac to gently apply vaccuum to the petcock to causes the gas to flow.

Then I would see how it runs, if it still has issues completely drain the tank. Remove the carbs and thoroughly clean them by taking them apart and cleaning the jets and tiny pin holes with a strand from a copper electrical wire. Be very careful not to damage the diaphrams under the black plastic covers. Things will fall out work over a container and draw diagramswhere the vacuum/ gas lines and little parts go so you have some hope of getting them back together right the first time. Be very careful not to knock the floats out of whack.
You need to use a spray cleaner, I use Honda carb cleaner and make sure you get it to flow out all the ports.

Im pretty sure that you will end up having to clean the carbs thats usually the reason they wont run right, they use such a small amount of gas that any restriction causes problems.

-Marcie

 

Wow marcie, thanks for such an indepth response. Now that you mention it, I have made the mistake of laying the tank on the ground [:'(]. Since the normal tank port on the petcock hangs lower, it is likely to be the one which collected dirt. I will take your suggestion and clean as much of the carb as I'm comfortable disassembling and if that doesn't do the trick I might have to take it to someone who knows what they are doing.

I'll try everyones suggestions and let you all know how it goes.

Thanks everyone! Wish me luck!

 

The carbs are very easy to clean. They are a complete pain in the **** to put back on the bike. So if you can get them off and back on you have accomplished the most difficult part.

Some things to keep in mind.

The screws may not come out, you will likely need to use a screw extractor. You can get new stainless meteric allen head screws at ace hardware.

Draw lots of pictures before you start taking things apart. This avoids the "where does this hose go" part.

Carbs arent rocket science you just have to get the bits back where they came from. Dont loose anything and be gentle, make sure the diaphrams get back in their seat.

Something to keep in mind, most shops just soak the carbs without taking them apart, this will not solve your problem you will have to have them taken apartto get all the particles out. In fact the 250 carbs can never be cleanedjust by soaking, thepassages are too tiny. Youwill save $ by learning to dothem yourselves theycan need to be cleaned often, depending on how long it sits.
I only trust myself to do it completely.
You can do it
-marcie

 

Ok I might give that a shot the next full day I can devote to it. thanks marcie.

Before I get involved with cleaning the carb. I was wondering your thoughts on carb cleaner fluid that you put in the gas tank? Since the bike has been running for several minutes before stalling, it seems viable unless it runs the risk of affecting the carb in a harmful way too. Also, is it unhealthy to run the bike on reserve for a long period of time? (in case I have to get this bike inspected before the problem is fixed).

I took the tank off again today and found some more things thatmay help to know. The rubber grommets (with ring of coiled wire) connecting the air box to the carberator were not sitting properly on the carb. I'm assuming they were bumped loose from the fall so I realigned them today. I removed the tube connecting the petcock and the carb and noticeda fewverytiny dirt particles in the filter at the end of the tube (which goes into the carb, but was stuck in the tube) and cleaned that. The element looked clean already.

Today, the bike, after the wild game of trying to play with the choke on warmup, ran good on reserve and a bit longer on ON once warmed up. I added gas just in case. I let it warm up on reserve, than switched toON and let it idle for 2 minutes before riding it for another minute in which it stalled. I switched the tank to reserve, started it and got moving then switched the tank back to ON. I drove it back to the house and let it idle with petcock set to ON for a good 7 minutes before it lost rpm and stalled again. I have yet to be able to start the bike with the petcock set to ON. Once warmed up, it always starts great while the petcock is set to reserve.