Strange Problem with Ninja

[blbills]

It's been a while since I've posted on the forums. My 2008 Ninja 250 has been absolutely flawless the past year and some change that I have owned it. I love this bike. It has had all of its scheduled maintenance with the exception of checking the valve clearances (I know, I'll get around to it.) Currently sitting at 7,800 miles.

However, just the other day it developed a very strange problem out of no where. It's also very challenging to explain fully. The bike will still rev though the entire range but when I release the clutch and start moving I only have power up to about 4000rpm. If I continue to push it past that it quickly cuts out and almost dies unless I feather the clutch. And again when I pull the clutch in I have no problem revving the bike though the entire rpm range.

You can only imagine how hard/dangerous this situation is. It takes about 30 seconds to get up to 50 mph and I've had to pull over a few times to let cars go by b/c I'm going so slow (pretty embarrassing). It seems like once I get up to speed that the rest of the rpm range is usable but a bit more sluggish than what I'm use to seeing.

At first I was thinking that this is a carb issue but I don't see how it could be when I can rev very cleanly all day long in neutral or with the clutch in.

I'm really at a loss on this one. Does anyone have an idea before I start tearing her apart?


Thanks!
Brian

[bob706]

Clutch slipping? Is your clutch cable adjusted properly?

[blbills]

I'm pretty sure the clutch is fine.

Wouldn't the rpm continue to climb if the clutch just wasn't engaging?

It's really weird everything is fine until you hit that magic 4000rpm (which actually happens rather soon on the 250 )

[setasai]

Wow, this one is a toughy. My first guess since it revs but doesnt produce power are the big 3: spark plugs, air, fuel. All of which is pretty easy to check. What you describe reminds me of before I shimmed the needles. It'd easily rev but there wasnt any power until 8k.

If you let the clutch out at 8-10k instead of around 4k rpms, does it exhibit the same power loss?

[kkim]

pull your plugs and see what they look like. this is a toughy.

if I had to guess, I'd say it's a carb or CDI issue, though I can't back any of that up as this is the first time I've heard of this problem on our bikes.

[Alex]

Fuel venting or fuel filter.

[blbills]

Alright guys,

Thanks for all the quick replies. I will look into each of those tomorrow when I have some light.

[setasai]

Goodluck. Keep us posted.

[blbills]

Update:

Well the bike left me stranded yesterday but that's another story. The bike will still idle and fire up just fine but now when I give it even a bit of throttle it cuts out and dies.

Checked the following and they seem to be fine:
Air filter
Spark Plugs
fuel lines
oil
coolant


Does anyone else have any suggestions before I pull the carbs? I really don't want to have to do that.

Someone mentioned a fuel filter but I don't see one anywhere?

[kkim]

Originally Posted by blbills

Someone mentioned a fuel filter but I don't see one anywhere?

there are 2. one in the tank as part of the fuel petcock and the other is at the end of the fuel line just before it enters the carbs.

what did the spark plugs look like?

[jstrain]

I had an old Camaro that behaved exactly like that. You were fine around town, but if you tried to accelerate up to highway speeds, it could barely stay alive. Fuel filter was full of junk.

I guess it could flow enough fuel to keep the engine happy at slower speeds, but once the engine demanded more fuel for higher speeds, it just couldn't flow enough.

[blbills]

Here's a pic of one of the plugs. They both look pretty much the same. They will both be replaced while I'm at it even though they aren't the problem.

I emptied the gas and checked the filter in the petcock and it was clean so my problem is further down the line.

Unfortunately it looks like I'm going to have to dig into the carbs.


...Unless anyone else can give me any more ideas...

I've done lots of dirt bike carbs but never a dual carb setup like this. Is there anything I need to watch out for?

[kkim]

check the DIYs in the new gen tech section. There are quite a bit of carb related threads.

http://www.ninjette.org/forums/showthread.php?t=5586

if you've worked on single carbs before you should be fine, except don't take the carbs apart from one another unless you really need to. work on them as one unit.

you have a PM.

[blbills]

I just still don't see how it could be the carbs. How likely is it that both of the carbs are gummed up in the exact same way? Wouldn't the bike be mis-firing and sound rough?

Instead it sounds perfectly fine when its running?

[kkim]

like I guessed in my original post, carbs or CDI. If you don't think it's the carbs, seriously consider the CDI. The new gens had some problems with the CDI when the bike was first released (they still do do to an extent). Most times it's just the tach reading that is erroneous, but I've heard of some people that had running problems due to bad CDIs. Find someone in your area that you could possibly swap it out with to troubleshoot.

[DaBlue1]

Is there anything blocking the air intake tube under the passenger seat area?
What have you done to the bike since it last ran fine? How do you ride (hard, easy) and when do you shift? You say it dies and around 4k but if you push past it it's seems like once you get up to speed that the rest of the rpm range is usable but a bit more sluggish than what you're use to seeing. Is this in all gears?
Does the bike feel like it is lugging in any gear?
What are the riding conditions like? Rain, snow, cold, wind, elevation

Here are some things that could be wrong.

Poor Running at Low Speed:
Spark weak:
Battery voltage low
Spark plug dirty, broken, or maladjusted
Spark plug cap or high tension wiring trouble
Spark plug cap shorted or not in good contact
Spark plug incorrect
IC igniter trouble
Crankshaft sensor trouble
Ignition coil trouble

Fuel/air mixture incorrect:
Pilot screw maladjusted
Pilot jet, or air passage clogged
Air bleed pipe bleed holes clogged
Pilot passage clogged
Air cleaner clogged, poorly sealed, or element missing
Choke plunger stuck open
Fuel level in carburetor float bowl too high or too low
Fuel tank air vent obstructed
Carburetor holder loose
Air cleaner duct loose

Compression low:
Spark plug loose
Cylinder head not sufficiently tightened down
No valve clearance
Cylinder, piston worn
Piston ring bad (worn, weak, broken, or
sticking)
Piston ring/groove clearance excessive
Cylinder head warped
Cylinder head gasket damaged
Valve spring broken or weak
Valve not seating properly (valve bent, worn, or carbon accumulation on the
seating surface

Other:
IC igniter trouble
Carburetor not synchronizing
Vacuum piston doesn’t slide smoothly
Engine oil viscosity too high
Drive train trouble
Brake dragging

Like kkim suggested, there may be a problem with your IC Igniter. I had mine replaced under warranty. They are not cheap, so see if you know if someone you can switch with to test to see if yours maybe bad.

[blbills]

Problem Solved!

After refusing to take the carbs out I tried a few more things.

Checked the vacuum system, checked for fuel when unscrewing the carbs drain bolts, etc... Nothing looked out of the ordinary.

Finally when I had things back together enough to start the bike I ran it in PRI (prime) mode on the petcock to see if there was any improvements. It seemed to get a bit better. So I started playing around with the hosing while it was just idling. I disconnected the second hose that comes out of the petcock (goes to the california emissions crap) and wallah! It came right back to life!

I really don't understand this as I had disconnected this hosing and inspected it when I took the tank off but for some reason while it was running when I disconnected it it solved the problem.

I'm ok with it. Beats taking the carbs out of the bike.

[blbills]

My problem is back!

It all of the sudden developed the same characteristics in a matter of minutes on the way home today and left me stranded!

Question, I'm trying to figure out the root of all of this and it seems like it may have started right after I filled up last month.

Now I can't really remember so I'm just fishing here but what if it was overfilled?
Could that cause any problems?


Thanks!

[kkim]

did you try popping the gas cap open to see if that helped the bike to start back up?

[blbills]

The bike actually starts and idles just fine. It's when I rev past 4000 that everything goes to crap.

[blbills]

Update:

Found that by turning the petcock to Prime that the bike runs just fine.

That leads be to believe that this problem is something to do with the vacuum system.