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Discussion Starter · #1 ·
I posted this over at the 250 forum.. and nobody ever really helped. Hoping that someone can help figure the problems out.

I just bought a 98 ninja 250. It runs fine when its started, but often gives quite a fight when trying to start it, when cold.

I just cleaned air filter, new plugs, valve clearances.

Before it would not really catch, but sometimes now it will start to start, and then wont keep running. I noticed that the #2 cylinder is not getting spark (screwdriver in end, close to ground). The header is not hot on that side either.

What could this be? Its quite annoying, and I put in the correct plugs for the bike.

I thought it was the sidestand problem, but I figured if that wasnt going to give spark, it would be to both cylinders, and only in gear.

I am using a charger/starter assisting the battery since it is just draining it while I keep trying to start it with no sucess. Anyone have any ideas?

After letting it sit for some time, I got it started.

The problem when it is started is... after it is a little warm, when you rev it, it will drop down to 2-3k and stay there. The only way to get it back down to normal(1k) is to turn the idle adjust screw until it drops, and then put the screw back where it was. The idle adjust screw Im talking about is that adjusting nut on the left side of the bike kinda under the fuel switch. Other than that, it works good, idles at 1k.

Any ideas? Im watching some of the rectifier/plug coils and other random stuff on ebay to swap it out and see if thats the problem, but I would much rather be putting money into the riding gear so I can actually ride it out of the neighborhood.
 

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second chimp in space
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Was it sitting for a while before you bought it?

Here's how you check for spark: you take the plug out, put the boot (wire) back on, and touch the outside of the plug against the engine. Then try to start it and look at the color of the spark. It should be bright white or blue. Red is no good.
It could be something as simple as corroded wires that need some cleaning. If the other spark is ok, I'd swap coils and see if the problem shifts to the other cylinder. That will narrow it down.

As for the idle, it could be dirty carbs. You can try putting some cleaner in there. Though the golden rule says to not mess with carbs until everything else works good, so get the spark issue solved first. Though the cleaner won't hurt anything, and may actually help a little.
 

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Discussion Starter · #3 ·
I think it sat for a little while, but not too long without being started. the carbs were just all cleaned, so they should be good. Could the carbs not being correctly syncronized do it? Not sure if that would be something that was already done or not.
 

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second chimp in space
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it might if they were really bad, but check out the spark problem first.
 

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Discussion Starter · #6 ·
Well I just went out and started it. It fired up the first time like a champ...didnt even crank over a few times, just started instantly. So hopefully it is going to keep doing that. The only thing I did differently was make sure choke was all the way on by pushing the actual slider.

So Im hoping that the valve adjustment/plugs/air filter helped it out.

I am hoping to have all my gear/tags/insurance by next weekend so I can do some early morning rides. But classes also start, so we'll see if I have the extra time to get it done.
 

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Discussion Starter · #7 · (Edited)
Aiighty, bump, I havent started it in maybe a week, and it just cranks. I took out the plugs, and wires, put against the head, and the spark was a blue/purplish. It was pretty consistant. So im not sure where to go from here. I did it on both sides, and they both looked the same.

Any other ideas?

edit: also tried with a battery charger, since I was just draining the battery and nothing. It didnt change a thing except it was trying to start much quicker.

I dont feel any heat on the header(s) at all. So maybe its not getting gas? I took off the seat, so the overflow little hose isnt crimped. I dont have a full tank, but should have enough. And unfortunately, cant ride it to the gas station, and ran out of gas for the lawnmower.

But I am pretty sure that its getting spark, since it did when i took it out. The sidestand switch is bypassed, so it cant be that. I tried adjusting the choke, throttle, and nothing.

Any easy things to check that could be gummed up between the tank and carbs? I might just take off the switch thing and the lines to it, and try to blow them out with some air. But other than that, I am puzzled. Of course, i just got gear, but nothing to do with it now. Go figure.
 

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Discussion Starter · #8 ·
I just tried again, nothing.

I do notice after I let it crank for a while, something sounds like it is gurgling. It'll do it for maybe 10 seconds after I stop. I am going to clean the tank I guess and hope for the best.
 

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Is there fuel in your float bowls?

It sounds like a carburetion issue. I would bet that your carbs need to be taken apart and cleaned.
 

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Discussion Starter · #10 ·
Redstar11 said:
Is there fuel in your float bowls?

It sounds like a carburetion issue. I would bet that your carbs need to be taken apart and cleaned.
Well, the carbs were supposed to be cleaned before it was sold.

As far as float bowls, im clueless, this is the first carbeurated thing I have had to work on. I am guessing that its inside it and i did that by flooding it? If so, I am probably guilty as charged.

If thats what they are, is this an easy thing to take apart? I think i need to go to howstuffworks.com and check out the good ole' carbeurator. think I spelled that wrong, but its 1:40 am.. its ok
 

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No, there is supposed to be fuel in your float bowls. They are at the very bottom of the carb. They will have a drain screw to check float level and such. Umm, It's going to be kind of hard to explain if you don't really know carbs that well. Take a look at this link

http://www.ronayers.com/fiche/400_0344/carburetor/carburetor.cfm?man=ka&groupid=6590&parent=6550

Look at the carburetor. The drain screw will be at the bottom of the picture next the the bowl. It's part number is 92009A. Try acessing those on your carb and watch for fuel draining out.
 

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Discussion Starter · #12 ·
Redstar11 said:
No, there is supposed to be fuel in your float bowls. They are at the very bottom of the carb. They will have a drain screw to check float level and such. Umm, It's going to be kind of hard to explain if you don't really know carbs that well. Take a look at this link

http://www.ronayers.com/fiche/400_0344/carburetor/carburetor.cfm?man=ka&groupid=6590&parent=6550

Look at the carburetor. The drain screw will be at the bottom of the picture next the the bowl. It's part number is 92009A. Try acessing those on your carb and watch for fuel draining out.
OK, thanks, I'll check it out a little later. So if fuel comes out, then that means I really am getting fuel, and its something else right?
 

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Discussion Starter · #13 · (Edited)
Well, I checked both, and they had fuel in them. One seemed a little bit more Yellowish than the other for the first few drops. So I am guessing that means I am getting fuel. What the heck could it be now ?? :(

Anyone? I tried draining some fuel out of the bowls and it didnt do too much. a few more times it attempted to start, would want to catch, but didnt stay running.
 

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Are the spark plugs brand new? How long ago did you put them in? I am guessing you just need your carbs cleaned. If it's trying to start, that means it's sparking, and you have fuel in your float bowls. So im guessing something is preventing the fuel from entering your combustion chamber efficiently, i.e. carb circuits gummed up.
 

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Discussion Starter · #15 · (Edited)
OK, yeah, thats what i was hoping now. Hopefully the manual I downloaded will be self explanitory for taking them apart.

But, when it was running, it didnt like sudden jerks of the throttle (not much) but gradual was fine, but if you did it quick when it was lower in the rpm range, it would kind of miss for a second. Could that be from the carbuerators as well?

Are they all pretty much the same design? Just take them apart and clean them? I know they were supposed to have been done not long before I bought it, but the air filter was pretty nasty, so I am sure it could have easily sucked up some crud. Who knows when I'll get around to it, but I would like to do it soon, and hopefully solve the problem.

Any tips/pointers for DIY'ing it? I'll search the forum to see if there are any threads for it.

Thanks.

edit: plugs were put in about 2 starts ago. After they were put in, and valves were adjusted and air filter cleaned, it fired up like a champ. And now nothing...
 

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All carbs are pretty simple if you know what you are doing. The carbs could definately cause the missing sensation you are describing with quick throttle inputs.

Some tips for carb cleaning. If you don't know what you are doing or looking for, don't do it. If you don't have an air compressor, don't bother.

You will want to completely disassemble the carb so just the body remains. You will want to spray carb cleaner through all of the circuits then follow it up with compressed air. You will also want to do the same to all the jets you removed.

If you feel it's going to be too much for you to handle, you can mail them to me and i'll clean them for ya for a small price. Otherwise, i'll help you out the best I over the [email protected] :beer
 

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Discussion Starter · #17 ·
Redstar11 said:
All carbs are pretty simple if you know what you are doing. The carbs could definately cause the missing sensation you are describing with quick throttle inputs.

Some tips for carb cleaning. If you don't know what you are doing or looking for, don't do it. If you don't have an air compressor, don't bother.

You will want to completely disassemble the carb so just the body remains. You will want to spray carb cleaner through all of the circuits then follow it up with compressed air. You will also want to do the same to all the jets you removed.

If you feel it's going to be too much for you to handle, you can mail them to me and i'll clean them for ya for a small price. Otherwise, i'll help you out the best I over the [email protected] :beer
We'll I've got a compressor, just havent ever done any carb work. I would say I am pretty mechanically inclined, just never had anything carbuerated to learn on, and always try to be careful the first time. I did my first engine swap 99% completely by myself with hand tools. So I like to learn how to do it, just dont want to end up breaking something the first time.

I might just watch ebay for now, and see if I can pick up an extra set used, and clean those, and just swap them out. Although I would really like to try and clean them this weekend, I need to start putting school first instead of waiting till the last minute...like I did last weekend and didnt do so well on my first quiz.

But thanks for all the help, hopefully this will solve the problem so I can enjoy riding finally.
 

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Discussion Starter · #18 ·
well, I took them off, wasnt too hard, but definately cramped. So heres the thing. This black thing that goes up and down (im guessing the choke) does not move up and down when I move the choke slider. It does move up and down by hand. Could that be a problem?




thats the one with the black thing


It looks like it has some crud in it, so I guess I will slowly take it apart. I have a printout of how it goes together, so hopefully I wont loose any screws/springs.



but you can tell it has to have been cleaned, just maybe wasnt put back right or something. It also had PLENTY of fuel, so thats not a problem.

thanks for any and all help.
 

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Discussion Starter · #19 ·
Well, I am not sure what to do now. I am pretty sure the plunger parts on the choke slider either dont have a good seal or are missing something since neither of them pull any vacuum for those choke butterfly things.

So now it looks as if I have a useless bike since I am sure these replacement parts prices are easily way too much to justify.

Anyone have an extra carb setup off a ninja 250? There are none on ebay. Guess I should have listened to everyone, and waited on getting a motorcycle :cry

One more thing gone wrong on this worthless weekend.
 

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Ha ha, Aero, the black 'plates' inside the carburetor are actually CONSTANT VELOCITY throttle slides. What you have is known as a CV carb. Your throttle controls the actual butteryfly plates. When you open those plates, you create a negative pressure inside the throat of the carburetor. This negative pressure (vacuum) will raise the "black slide" and allow the atomization of fuel via de-restricting airflow and controlling the jet needle/needle jet.

To clean them, you will want to remove the float bowls, the bottom part of the carb. That will expose your floats, and your jets. You will want to remove both. Once you have done that, you will want to flip the carb back over, and remove the vacuum slide and rubber diaphragm. That black plastic cap on top will kind of pop off once you remove the screws because there will be a spring in there that helps control the movement of the CV throttle slide. once you remove it, pull out the throttle slide and jet needle. From there, you can start blasting carb cleaner through every hole you see in the carburetor body. Follow it up with a blast of compressed air. You will want to do this twice. Watch the carb cleaner as you are spraying it through the circuits and observe it coming out of a different hole in the carb body.

If you really do get stuck, just mail those suckers to me and i'll take care of them for ya. good luck :beer
 
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