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Discussion Starter · #1 · (Edited)
So I bought my 2008 Ninja 250 Monday, everything was perfect and loving it. Last night me and my friend who is a mechanic took it apart and looked for any missing nutes and screws and checked out what we will fix next time I bring it over. The only thing mechanically we did though other than remove the fairings was remove the air filter which was dirty as can be. So we put it back in and noted that we will change it asap. Well today on my way to work I am pulling up to a red light and my bike shuts off, I thought I had stalled it like an idiot but then it wouldn't turn back on. It wanted to start but just didn't have quite enough umph in it to start. So I roll it into my parking space 300 feet away and go to work, I come back after work and play around with it.

Here is what I discovered, I have to have the choke out nearly all the way or else it will die on me. The throttle control switch on the side does exactly, nothing. Doesn't matter how far clock wise or counter clock wise it does nothing to control the throttle. I have to have the choke out nearly all the way to get it to turn on all the way, if I leave it all the way out it idles at 3k RPM which seems a bit high. I then played with it and I can only slightly put the choke in and it will idle around 1-1.2k RPM. Now I can ride perfectly with it like this, although once I did have it die on me much the same way it did the first time because the RPM just kept dropping and it shut off. I am concerned that riding with the choke out is bad since I have read a few people saying that it isn't good for the carbs or something.

My question is since we removed the air filter and might have put it in backwards and its sucking all that junk into the motor or something, or could it just be the air and gasoline mixture be causing this because the air filter is dirty? I tend to believe the air filter is mainly the issue since it was fine the first 2 days and I rode it 200 miles and it drove like a champ and it wasn't till the next day after it happened. Any mechanics or people with this sort of experience have any ideas?
 

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You did something wrong during reassembly.

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Discussion Starter · #4 ·
How easy would it be to check the vacuum line, soap and water? I have my K and N filter in the mail now and only riding it to and from work till I get it and take it all apart. Just wondering if the vacuum line is some obvious line or something difficult to get to and check.
 

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Mine was exactly the same way. First off you don't have to change the air filter, just clean it. Second, adjust your idle speed. Should help a lot. Clean your carbs - change fuel filter - make sure carbs are synced. Also, change your plugs. They're probably fouled. Ninja 250 carbs are an annoying pain in the ass if the idle is not properly adjusted, they are dirty, or not in sync.

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Discussion Starter · #6 · (Edited)
Do carbs usually just clog up all of a sudden like that where they stall the bike without any real warning?

I have tried adjusting the idle speed however right now it doesnt matter how much I turn it in either direction it does nothing to change the idle speed when i have the choke open, I can't get it to run without it open so that is an issue right now. The air filter is already in the mail and will be here tomorrow, I took it out and tried blasting it with compressed air and beating it out to no avail, I just said screw it and bought one last night. Also tomorrow me and my friend are going to replace the fuel filter, I hope that fixes it because I was planning on cleaning the carbs and all that but not this weekend. Would using Seafoam be worth it, or just say screw it since I am already planning on cleaning the carbs this weekend?

Also how bad is it to ride around with the choke open? I cannot imagine it would be too good for my bike, right now i am just using it to get me back and forth from work with no extra trips in between until we can get this fixed.
 

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If the choke needs to be on to keep it running, the mixture is way too lean. If it ran good before, and now it doesn't, something is plugging up the fuel flow. Pinched fuel line? possible, but not likely. Most likely is crud in the carburetors. Answer: Think CLEAN my friend, Clean the carbs, new air filter (since you have one on the way) Clean intake tubing, Clean fuel, Clean filter screen and petcock valve, and be sure there are no chunkies floating around in the tank.
 

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They dont clog all of the sudden, it happens over time and then all of the sudden something along the lines of a stuck float or clogged jet happens which causes you to stall.. many things cause it including running low on fuel, running old fuel after the bike has been sitting, running cheap fuel etc, its not a matter of if, but when your carbs will get dirty. Seafoam might help, but since you're planning on removing them and cleaning them, I'd recommend Berryman b-12 chemtool for that.

I did a lot of research because I rode with the choke on for a long time, there's two major concerns and those the fouling of the plugs, and I also heard from someone on this forum that over time riding with the choke open will cause your oil to be contaminated with gas, which is bad of course, so keep an eye on your oil level and if it seems that it's higher than normal, do not ride or start, just change your oil asap.

The proper way to adjust your idle speed is with the bike fully warm, choke off. I've heard that the idle speed adjustment should ideally follow a proper valve adjustment, which I believe is to be done once at the 500 mile service and every 6000 miles following that. If it won't idle or idles really rough, a valve adjustment might be something to consider, although it won't solve your problem it'll help you accurately adjust idle speed. The ninja 250 is supposed to idle between 1 and 1.5 rpms

If you need any good information on how to properly perform any of that maintenance, ninja250.org has a ton of very detailed tutorials on maintenance and repair. Helped me a lot.

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Discussion Starter · #9 · (Edited)
Well I went and got half a pint of Seafoam and put it in my tank, road around for about 25 miles and realized I was hitting rush hour so I said screw riding in this for right now. I will try again later after work, I got my new air filter and greased it up and slapped it in. So far it still isn't able to run without the choke.

Next week me and my friend are going to clean the carbs, after running some seafoam in the system I can now set the choke back enough that it idles steady at 2k RPM; still not good but 1/3rd better at least. So far after cleaning the carbs I plan on changing the spark plugs to NGK CR8E, changing the motor oil to Shell Rotella-T 15w40 and changing the oil filter while I am at it. I do have one question though, I have been reading online and some people have been removing the OEM fuel filter and replacing it with ones that go on riding lawn mowers and such because they say it is better. Is this true, and if so is it cheaper or more expensive?
 

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I've heard that some ninja 250s do not come stock with a fuel filter, not sure how true that is but.little clearview inline 1/4 or 3/8 inch inlet and outlet fuel filters are pretty standard for small engines, dirtbikes, lawnmowers, snowblowers etc. They can be found at any parts store and are extremely cheap. Think like $2 or $3

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Discussion Starter · #11 ·
So today I removed my cheap inline Fuel Filter and installed a brand new one using the directions from this website How do I install a fuel filter? - Ninja250Wiki. Started right up and worked just as well as before, unfortunately I still have to use the choke to operate my motorcycle. So after doing nearly everything that has been suggested to me it looks like it is my carbs that is causing the issue, or so I hope. Hopefully next Sunday I will be able to post on here that it went well and cleared everything up, thanks for all the advice!
 

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How often have we seen posts like" ......Me and my friend who's a mechanic.......something doesn't work anymore............"?

If you just need a tiny bit of choke it's possible that your throttle stop screw and/or idle mixture screw needs adjusting. With the engine fully hot you should be able to set idle properly irrespective of other issues with the fuelling. Replacing the dirty air filter will have leaned out the mixture, so you'll need to readjust to suit.

What are you using to adjust the idle?

Rob
 

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.... I have been reading online and some people have been removing the OEM fuel filter and replacing it with ones that go on riding lawn mowers and such because they say it is better. Is this true, and if so is it cheaper or more expensive?
The 2008+ Ninja 250s have a micro screen on the petock inside the tank and a inline filter inside the carb nipple. Unless you live in a dust bowl and the gas you buy is from low grade gas station with outdated filtration on the pump, it's highly unlikely you're going to be filling up your tank and carbs with dirt. Your bike is only four years old so, keeping the gas tank full with fresh gas will also help with any flash rust that may happen inside the tank if you live in an area with extreme temps changes/high humidity.

An inline filter on a new gen IMO is not necessary and the wrong or improper hose length can cause a fuel flow problem. If the fuel filter can not stay full with fuel while the bike is running, it is the problem. Just remove it and see if the running condition improves. If the bike was running fine before then all of a sudden it does not, ask yourself, "What did I add or take away?", then reverse it.

The other thing I noticed is you said, "So I bought my 2008 Ninja 250 Monday, everything was perfect and loving it.", "....I have to have the choke out nearly all the way or else it will die on me. The throttle control switch on the side does exactly, nothing." ".... I tend to believe the air filter is mainly the issue since it was fine the first 2 days and I rode it 200 miles and it drove like a champ and it wasn't till the next day after it happened."

How long did the bike sit before you bought it and did it really run all that perfect to begin with. My guess is, it did not run as well as it should when you bought it. If the bike set without running for a while, your carbs may need cleaning. Until you do that, you will have problems.
 

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Discussion Starter · #14 · (Edited)
Unless you live in a dust bowl and the gas you buy is from low grade gas station with outdated filtration on the pump, it's highly unlikely you're going to be filling up your tank and carbs with dirt.
I live in Arizona and we have already had 2 major dust storms and some smallers ones, so yes I do live in a dust bowl for the most part lol. Got caught in a minor one yesterday while on the freeway actually, forced to pull off and go into a Circle K for a couple minutes. Also the previous owner used it as his main form of transport to and from work, he put over 12k miles on it himself in a 2 year period so I know for a fact he didn't let it sit because I ran a VIN number check on the bike before I bought it.

Well it was running perfect till I ran out of gas, the fuel gauge needs replaced and I was riding it hard. Like 100MPH hard the first 2 days I had it, I forgot to calculate the fact that I was riding it much harder than when they do the MPG equation and when I ran out of gas I filled it up and that is when I started having issues. Before that it was literally perfect, figure when I ran out of gas it caused some crud to be sucked into the carbs and that could be what's wrong. Unless anyone else thinks other wise.

Also since I am due for an oil and oil filter change which I have sitting in my garage is it worth waiting until after the carbs are cleaned or just do them tomorrow?
 

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...You didn't say that you'd run out of gas.

You may well have some crud in your carbs or fuel filters now.

Rob
+1. Also to to mention there is a possibility you may have gotten some small amount if water as well. You may want to drain the float bowls, check/cleanthe inline filter on the carb, get some fresh gas, add some Star Tron Fuel Treatment (@Walmart), prime your carbs, then see if that cures your problem and hope your carbs are not badly clogged. The air filter should help, but living in the conditions you do, more frequent air filter cleanings is a must.
 

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Discussion Starter · #17 ·
Yeah, I went to send it on my phone about running out of gas but it never sent for some reason and I checked last night about my reply and noticed it wasn't there.
 
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