Acceleration Issues and Finicky Idle

[Kotite]

So I bought this bike and appear to be the third owner, it is a 2005 Ninja 250. The previous owner never had the oil changed and had it 4 months, the chain was (and unfortunately still is ) filthy. So I had noticed a few issues with the bike in the first week riding it, including it dying after going up and down hills, though it could be considered just random dying. I emptied the oil (filthy) and replaced the filter and oil. I then noticed a recurring issue with my throttling, where I would have dead patches in which adding more throttle either lowered the RPM's or simply kept them in the same place for a few seconds before quickly climbing. The issue is prominent at lights where iw will quickly climb to maybe 3k or 5k but then die back down to 2k, I hold the throttle down until it finally catches and quickly climbs to 8-10k at which point I am able to shakily upshift and accelerate off.

Cruising it uneasily keeps RPM, jumping about for 250-750 rpm's in either up or down. Idling it idles low even with So-Cal weather so I keep the choke on for a minute or so then let off and it will sit at 2k.

I've taken the bike to a mechanic I trust to ask him to sync the carbs and he pointed to my oil gauge. He asked me to turn on the warmed up bike, and we saw the oil gauge oscillate and bubbles appear as oil flowed about. He said that's likely gas getting into the oil and the issue would be my piston rings (to get those fixed is 1200 -- I payed 1400 for the damn bike). So he told me to give up. Issue is, my dad and I have removed my oil cap and smelt it -- no smell of gas. Also, we would have noticed the stench when dumping the oil, as the bike had this throttle issue before we changed oil. IMHO there is no fuel getting into the oil reservoir but there are undeniable bubbles and oscillations.

This is what I've done:
-Changed oil
-Changed oil filter
-Ran without the air filter as a test (no difference)
-Turn the petcock to off overnight before riding
-Cleaned the carbs (yes every part down to the holes by the butterflies and the jets)
-Adjusted the black, outer idle control on the carbs after the bike had warmed up
-Checked the fuel filter (was clean, still is clean)

Open to any and all opinions, I've been scrounging about this forum and possible solutions I've seen include a valve and carb sync (in that order), petcock replacement (though I don't see fuel leaking).

Additional deets:

When first getting the bike, I assumed it had an empty reservoir (looked into the oil area through the cap and it looked empty) so I poured oil into it. Must have overfilled it, as I did this when it was warmed up and there was likely oil in the block and not in the reservoir (didn't know). When I drove a few miles from the Cycle Gear and parked the bike, I noticed the air box hole had leaked a ton of oil down onto my chain and kickstand. Two days later I replaced the oil.

[csmith12]

Welcome Kotite!

Hope you can get ti figger'd out.

[Yamahawk]

Hi Kotite,
I know these problems can be frustrating to figure out, but if you take one step at a time, it should be able to be conquered!
The carburetors may be leaking by the float needles, hence the gas in the oil. I do not think your mechanic was correct about the rings being the problem. Chances are (as Johnny Mathes once said) it would be carburetor related. Anytime there is an issue with gas, it is your carbs, or the petcock. If you combine both, you can actually have an amount of gas that leaks from the petcock, and then runs through your float needles, and if the bowl vents are not working/clogged etc. can end up with a cylinder full of gas. (Kawasaki Concours are notorious for this, leading to the dreaded hydrolock of the cylinder, and a bent con rod). I would make sure that your carbs are working properly, and that means taking them off and servicing them. There is a fellow in this forum, that advertises carb work, and he is reasonable. Check the Merchandise Section, and if you are not absolutely sure that you can do the work, send them to him.
Your dead spots are carb related also, and everything except over-filling the bike with oil, should be also carb related. Do your carbs have the caps over the idle mixture screws still? If so, then you didn't clean the idle circuit well enough, as these have to be removed to service that passage.
Sometimes, when we do something like overfill with oil, (yes I have done that lol) it can lead to things getting oil filled also, I would check all your breather tubes, vacuum lines, etc for oil and try to clean out as much of the oil as you can find. It may clear up with continued running, but if not, then try the carb route. Now, I notice you mention an oil gauge. Is this something the P.O. added at some time? There is a sight glass where you check the oil level when the engine is off, and yes there should be oscillations and bubbles noticed there when running the engine... You should NOT see an oil level with the engine running, as that oil is being pumped around your engine by the oil pump.If you do, then your engine is overfilled with oil. Hope you get it sorted out!
Charlie

[Kotite]

Originally Posted by Yamahawk

The carburetors may be leaking by the float needles, hence the gas in the oil.

Oh that's good to know about the oil, by gauge I meant that little window haha. Dang pulling out these carbs was a pain the first-time around, not looking forward to doing it again. In California there should be caps on those screws but I noticed they weren't there the last time I pulled off the carbs. I hadn't heard of how to properly adjust them at the time of the cleaning so I left them be. Guess now that I know about the 2 1/4 turns out rule, I will pull them out and clean that.

So aside from pulling out those mixture screws and cleaning them, what other parts of the carb need to be looked at again? I cleaned the little holes by the butterfly, the walls, the main jet, pilot jet and the bobber things. Is there an easy way to pull out those needles to clean them?

[Kotite]

Originally Posted by Yamahawk

Hi Kotite,
hence the gas in the oil
Charlie

Also worth noting that I just took the bike out, rode it around and then took the cap off of my oil reservoir and smelled it. No trace of gas. Also if the carbs being dirty is the cause of this alleged fuel in my oil, we would have smelled it when we replaced the oil which we didn't ...

[Motofool]

Originally Posted by Kotite

.......... Open to any and all opinions, I've been scrounging about this forum and possible solutions I've seen include a valve and carb sync (in that order), petcock replacement (though I don't see fuel leaking)..........

Welcome, Kotite !!!

What your bike is doing is not only abnormal but is very dangerous to be ridden in traffic.

Is this your first bike?
Are you experienced doing simple mechanical work?
Do you have the conditions to do such work?

You have many mechanical problems and one mechanic, who has demonstrated to us that he is not the solution to any of those problems.

[Yamahawk]

Originally Posted by Kotite

Also worth noting that I just took the bike out, rode it around and then took the cap off of my oil reservoir and smelled it. No trace of gas. Also if the carbs being dirty is the cause of this alleged fuel in my oil, we would have smelled it when we replaced the oil which we didn't ...

OK! That is a good thing. check out @ducatiman in the Motorcycle related area, he has some good suggestions as to what can and will be problematic on these carbs, especially the vacuum connections between the two carbs. When you pulled them off for cleaning, did you separate them or leave them bolted together? It is not the carbs being dirty that gets the gas in oil problem, it is wear of the float needle/seats. The float needles are under the tang of the float, in each carb, and the float presses them up into the seat, hopefully sealing them. The constant vibration of an engine running, will cause these to were, and not seal well. Of course, dirt CAN be the problem here also as the needles most likely have a viton tipped needle, which can trap dirt particles causing the gas to leak by. I believe that your problem is carb related, as it is the most likely place for your symptoms to start.
Now for the oil sight glass... on the center stand, look at the glass window with the bike off, and setting for a few minutes for the oil to settle, and see where the level is. You will notice level marks next to the window, and the oil level should not be above the top mark. Anywhere in between those marks is good, however. If it is above the window, the oil level is too high, and you should drain some out.
The carb parts that I would clean, would be the idle mixture screw passages, the NEEDLE JET, make sure you pull it all the way out and clean all the little holes in the side of it, float needles and seats, and the pilot jets and passages. Make sure the float levels are spot on also, this is a big part of a good running set of carbs. I am sure there are other passages, and those all should be verified to be clear. Anywhere there is a hole or passage should be shot with carb cleaner or compressed air, and you should see another area it shoots through and out of. If not, it could be plugged. I hope this helps!
Ducatiman may be able to give you some help here, also.
Charlie

[Kotite]

Originally Posted by Motofool

Welcome, Kotite !!!

What your bike is doing is not only abnormal but is very dangerous to be ridden in traffic.

Is this your first bike?
Are you experienced doing simple mechanical work?
Do you have the conditions to do such work?

First bike; I've been doing work on old VW's since I was maybe 4-6 with my dad, and I'm 18 now, so aside from that nothing with bikes; I do have conditions, tools etc. although I don't have the more specific instruments needed to sync the carbs or adjust valves.

I agree it is both abnormal and dangerous, it's a worry I have to consider at every light and turn. Basically going from a stop up to speed with traffic is arduous if not all-together impossible at times. The bike doesn't want to accelerate, it has a flat in its throttle and won't go past certain rpms. Sometimes I have to sit there and hold the max throttle until it catches.

[Kotite]

To re-iterate, I have smelled the oil, cap and reservoir and there does not seem to be fuel in the oil. I have the carb out now, just got done removing it, I'll check those screws and adjust them as well as look at those needles and the float / seating. I'll have to dig up that post on the wiki about correctly setting the float and the little thing that rests on the gas part but that'll be in a bit. The oil returns to the glass usually at the normal level or slightly above it, I have a re-threaded oil cap thing that sweats so I just top off the oil beyond that level for good measure. I'll check out this Ducatiman dude right now.

[Yamahawk]

Remember to pull the needle jet/emulsion tube that the main jet threads into. That is one area that gets neglected during a carb cleaning, and is important for the air jet in the carb intake bell to emulsify the fuel into the air correctly.

[Kotite]

Originally Posted by Yamahawk

needle jet/emulsion tube that the main jet threads into.

Do you have a picture of this inside of the carbs so I know where it's at? Sorry I'm more of a picture kinda' guy haha.

[Yamahawk]

That's cool, I do not have one, but have seen them here on the forum, and I have an 86 service manual. You will have to pull the top cap and vacuum diaphragm and slide with the needle in it. Then pull the float bowl, and remove the main jet - then unscrew the needle jet/emulsion tube from the bottom of the float bowl area, and remove it. (sorry, i was thinking of my other carbs lol), . There could be some corrosion in it that keeps it from moving at first, try not the damage the threads for the main jet when pulling it out. You will see it inside the bore when you look from the intake side, it is where the needle drops into when the slide is down. Make sure all the small holes are clean in the sides of the tube.

[Motofool]

Originally Posted by Kotite

First bike; I've been doing work on old VW's since I was maybe 4-6 with my dad, and I'm 18 now, so aside from that nothing with bikes; I do have conditions, tools etc. although I don't have the more specific instruments needed to sync the carbs or adjust valves.

I agree it is both abnormal and dangerous, it's a worry I have to consider at every light and turn. Basically going from a stop up to speed with traffic is arduous if not all-together impossible at times. The bike doesn't want to accelerate, it has a flat in its throttle and won't go past certain rpms. Sometimes I have to sit there and hold the max throttle until it catches.

The bike needs to be stopped and receive a full service, like if no maintenance work has been done on it.

I see that you are concentrated on the oil and synchronization of the carbs, but there is much more in need of attention.
There is a screen filter upstream the paper oil filter that should be cleaned during oil changes, but it can be done next time.
The oil level should be checked only with the bike on both tires and perfectly vertical and with the engine off.
No smell of gas or non-increasing level means that fuel is not currently leaking into the crankcase, where the oil is collected.

Synchronization of the carbs is nice but the engine can function perfectly with imperfect sync; hence, not the most important thing about carburetors.
Adjustment of valves, fuel supply, chain, tires and brakes are far more important.

I recommend you doing all the work yourself because with the experience and conditions you have, nobody would do it better than you.
Follow these links, don't get intimidated and have fun:

http://faq.ninja250.org/wiki/Ninja250_Howto

http://faq.ninja250.org/wiki/Service_Schedule

http://faq.ninja250.org/wiki/Intake

http://faq.ninja250.org/wiki/How_do_...n_the_carbs%3F

http://faq.ninja250.org/wiki/Carburetor_photos

http://n4mwd.blogspot.com/2013/10/se...-passages.html

[Kotite]

Originally Posted by Yamahawk

That's cool, I do not have one, but have seen them here on the forum, and I have an 86 service manual. You will have to pull the top cap and vacuum diaphragm and slide with the needle in it. Then pull the float bowl, and remove the main jet - then unscrew the needle jet/emulsion tube from the bottom of the float bowl area, and remove it. (sorry, i was thinking of my other carbs lol), . There could be some corrosion in it that keeps it from moving at first, try not the damage the threads for the main jet when pulling it out. You will see it inside the bore when you look from the intake side, it is where the needle drops into when the slide is down. Make sure all the small holes are clean in the sides of the tube.

I've cleaned the main jet bit last time I cleaned the carbs, but never removed that top black cap that houses the spring and diaphragm. I'll pull those out and do that I suppose.

I just pulled out the idle adjustment screws and the springs inside and they were bloody filthy. The PO who removed the EPA caps from these screws must have basically screwed (in the bad way) the needle things, because they are filthy.

[Yamahawk]

Originally Posted by Kotite

I've cleaned the main jet bit
This is not the needle jet/emulsion tube. The main jet screws into it, and you need to wrench it out after you take out the main jet.It is two pieces, the main jet and the tube it screws into must be removed also.
last time I cleaned the carbs, but never removed that top black cap that houses the spring and diaphragm. I'll pull those out and do that I suppose.

I just pulled out the idle adjustment screws and the springs inside and they were bloody filthy.
This is one reason for your poor performance.
The PO who removed the EPA caps from these screws must have basically screwed (in the bad way) the needle things, because they are filthy.

Actually, they are filthy from sitting with gas in them for an extended period of time. Gas gums up, then attracts grunge.

[Kotite]

Originally Posted by Motofool

The bike needs to be stopped and receive a full service, like if no maintenance work has been done on it.

I recommend you doing all the work yourself because with the experience and conditions you have, nobody would do it better than you.
Follow these links, don't get intimidated and have fun

Ha! Well thanks for this, I'll have to knock things on that service list out one at a time. PO didn't do anything and the guy before him told him "Kawi's are easy just ride it into the ground, it ain't worth the cost of service" soooo it is safe to assume I need to do everything. Kid put sparks in though so I mean, he did something.

Not sure if I can do everything here, as I have no idea how to tighten the chain, change my sprocket or stuff like that. I plan to keep at motorcycles so maybe I'll invest in these tools but for now I need to get this bike in a ride-able state. These carb pictures and that last diagram you linked are rad and I will be using em' right now alongside the parts diagram Kawi has online.

While I have the carbs out, anything else I should do that they get in the way of? Air filter seems clean and damp with good oil, so that seems fine. I've drained the airbox drain tube which was filled and unsurprisingly disgusting. He probably replaced this filter or someone did, it seems new-ish.

[Kotite]

Originally Posted by Yamahawk

Actually, they are filthy from sitting with gas in them for an extended period of time. Gas gums up, then attracts grunge.

I see, alrighty. I mean the bike probably hasn't sat much between me and the two PO's I can trace it back to but it makes sense. This filth seems more like tarnish then gas gum though.

Also, like I said before, without pictures I don't really know what you're talking about, but I'll be yanking that diaphragm and spring and working on that. I'll also look to see about removing that housing for the big jet if that's what you mean.

[Yamahawk]

Originally Posted by Kotite

I see, alrighty. I mean the bike probably hasn't sat much between me and the two PO's I can trace it back to but it makes sense. This filth seems more like tarnish then gas gum though.

Also, like I said before, without pictures I don't really know what you're talking about, but I'll be yanking that diaphragm and spring and working on that. I'll also look to see about removing that housing for the big jet if that's what you mean.

Yeah, the part that the main jet screws into is the part you need to unscrew and pull out. It should be about an inch or more long, and about 6mm in diameter or so, it should have a hex wrench area on it, when the main jet screws into. The main jet could have either a screwdriver slot in the top of it, or a hex also. look at it carefully, to see what it is. As Motofool said, do your own work, and learn from it. i screwed up a few things while I learned how to do my own work, so don't feel bad if you do mess up, everyone does.

[Kotite]

Originally Posted by Yamahawk

Yeah, the part that the main jet screws into is the part you need to unscrew and pull out. It should be about an inch or more long, and about 6mm in diameter or so, it should have a hex wrench area on it, when the main jet screws into. The main jet could have either a screwdriver slot in the top of it, or a hex also. look at it carefully, to see what it is. As Motofool said, do your own work, and learn from it. i screwed up a few things while I learned how to do my own work, so don't feel bad if you do mess up, everyone does.

Ah this little metal bit with a hump in the middle, got it. Looks clean but never got to it, interesting. I had cleaned the main jet, I just didn't know this thing was in it.

So at this point I'm cleaning that, the big-@$$ needle that came out of the diaphragm and then the springs and idle mixture bits I pulled from the idle mixture cavities. I've also re-checked the small holes by the butterfly valves as well, and they seem good to go.

[SLOWn60]

Welcome Kotite
These bikes are very easy to work on and only need the most basic of tools. Your experience working on VW's well qualifies you to do virtually anything yourself. The links above and a few YouTube searches will give you all the technical info and visual info you need. Removing the carbs is a royal pain but even that isn't too bad after you've done it a couple of times!
Good luck and have fun tinkering!
But do make sure all your systems are operating safely before throwing yourself into traffic!

[Yamahawk]

Originally Posted by Kotite

Ah this little metal bit with a hump in the middle, got it. Looks clean but never got to it, interesting. I had cleaned the main jet, I just didn't know this thing was in it.

So at this point I'm cleaning that, the big-@$$ needle that came out of the diaphragm and then the springs and idle mixture bits I pulled from the idle mixture cavities. I've also re-checked the small holes by the butterfly valves as well, and they seem good to go.

Here is a link to the Parts finder for your carburetor, the needle jet holder #13091 and part #16017, needle jet, is the part I was referencing.

http://www.partzilla.com/parts/searc...RTS/parts.html

[jkv45]

Take some time and read through this section if you haven't -

http://faq.ninja250.org/wiki/How_a_c...arbs_explained

This is the assembly with the needle jet and jet holder/emulsion tube that the Main Jet screws into -

http://faq.ninja250.org/images/e/eb/Jim_carb_2.jpg

Also be sure to clean the passages for the idle mixture, and confirm the idle mixture screws have an o-ring and washer on them before installing them and setting to 2.5 turns out as a baseline.

[Motofool]

Originally Posted by Kotite

Ha! Well thanks for this, I'll have to knock things on that service list out one at a time........

You are welcome

Originally Posted by Kotite

Not sure if I can do everything here, as I have no idea how to tighten the chain, change my sprocket or stuff like that. I plan to keep at motorcycles so maybe I'll invest in these tools but for now I need to get this bike in a ride-able state.........

Keeping a good chain clean and lubricated will reduce the number of times that you will need to slide the wheel back to compensate the chain's slack.

https://www.ninjette.org/forums/showthread.php?t=133019

Again, following those links and using basic tools, all service work is simple.

Originally Posted by Kotite

While I have the carbs out, anything else I should do that they get in the way of? Air filter seems clean and damp with good oil, so that seems fine. I've drained the airbox drain tube which was filled and unsurprisingly disgusting. He probably replaced this filter or someone did, it seems new-ish.

Check that the slides can move up and down freely using your fingers; sometimes accumulated dirt interferes with that movement.
Be very gentle removing the covers of the diaphragms, keep then attach to the body and detached from the cover; they are made of thin Neoprene than can be easily damaged during manipulation.
The diaphragms need to pull and push the needles; hence, keep the assembly in the same order than what you find.
There is only one position for the metal steel guide of the needles.

[HoneyBadgerRy]

I recommend giving the carbs a good cleaning, and while you have the carbs off, shim the needles, and give the throttle cables a good lube, make sure that the slides are free moving.

[Ghostt]

My 2¢,

Considering the age of the carburetors, I personally recommend getting them fully refurbished, not a cleaning, PM @ducatiman for all your carburetor needs, you'll find his prices are extremely affordable.




https://www.ninjette.org/forums/showthread.php?t=226815

If you insist on DIY, then he'll sell you very complete rebuilding kits.



As far as synchronization method, use the bench synchronization method, and set the float height.

Don't forget when you do the spark plugs, to service the spark plug caps as well.

[Kotite]

Hi sorry that I haven't responded! After cleaning the idle mixture screws and resetting them, the bike no longer has any issues. Thanks everyone for the advice and links.

Next thing I'll have to do is a valve adjustment and after that a carb sync, I'll be reading through the forum for info on that! Thanks everyone.5

[Ghostt]

Valve adjustment yes, carburetor synchronization no, service the spark plug caps yes.

Then tune the idle mixture screws.