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Discussion Starter #1
Hello Everyone, the other day i was in a group ride cruising at about 70+MPH then all of a sudden out of nowhere my bike started to sputter almost like it wasn't getting enough fuel even though I had a full tank. I had a total power loss from 70 to 55 mph while i was WOT (wide open throttle)

We pulled off of the highway for about an hour for a break, I had to leave due to this problem and rode home WOT in 6th gear at now 65 MPH. This problem comes up whenever I try to accelerate really fast. It will get to around 9k RPM and then just completely sputter and bog down, then the power surges up and down. I have been researching this problem for the past two weeks and I have yet to find a fix to it.

Things I have tried:

-Seafoamed the gas tank
-Seafoamed the carbs
-Replaced the CDI/ECM (some people also call it the IC [ignition controller]
-Replaced the spark plugs (the old ones were crap anyway)
-Cleaned the air filter
-Went for slow cruises around town
-Tried "gunning it" (accelerating as fast as I could)
-Checked the petcock (fuel is definitely flowing)
-Checked for loose electrical plugs/vacuum hose issues

Things I have noticed:

-The Rev limiter is no longer working (if I WOT in neutral or even first gear i get nothing, it will just dive straight into the red zone [i never hold it there for long, it never did this before])

-Problem occurs around 9k RPM

-Idle is still good, torque is still good

BIKE SPECS
*2008 Ninja 250
*17000 miles
*Two Brothers Slip On Exhaust (been running fine for a year and a half after I installed this)
*Unleaded fuel trying premium after this issue popped up
*Well Maintained


I desperately need help, I have looked everywhere and tried almost everything. I have been to about 6 different forums but no luck at all. So I am making this thread here, hopefully you guys can help me fix this, and some other poor soul could use this as a reference. Any help will be appreciated and I will update this thread with any changes. I am at my wits end any help will be appreciated thanks!
 

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Discussion Starter #2
Similar thing has happened to me. On a trip where it was raining and lots of condensation. If you haven't already, drain the bowls and the old gas from the tank. Put in fresh gas. Try and post back.
I gave this a shot yesterday when I seafoamed the carbs. Nothing but fresh gas in there now. Still no dice :( Thanks for the quick reply though.
 

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Discussion Starter #5
What mods do you have on the bike?
I had something similar happen to me before.

Not sure why you changed the IC Ignitor seeing it was working ok before the switch. Sounds like a fuel delivery problem.
Do you by chance have a inline fuel filter installed?
Have you checked the stock fuel filter in the carb?
I also would not use premium if you have fresh gas already. 87 octane works best.
Air Filter: Has been cleaned, a new one would be better though

Mods: Everything on the bike is stock, except the two brothers exhaust, which was installed a year and a half ago and has been deemed not a part of the issue

The stock fuel filter is SPOTLESS
 

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Air Filter: Has been cleaned, a new one would be better though

Mods: Everything on the bike is stock, except the two brothers exhaust, which was installed a year and a half ago and has been deemed not a part of the issue
Kawasaki recommends replacement of the stock filter @ 2 years. Old filters tend to compress. IMO any air filter is better than stock. I found the Pipercross air filter to flow really well for a foam filter.

No shims or snorkel removal to go along with the slip on?

Also, if your rev limiter is not working, your IC Ignitor is bad.
 

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Discussion Starter #7
What mods do you have on the bike?
I had something similar happen to me before.

Not sure why you changed the IC Ignitor seeing it was working ok before the switch. Sounds like a fuel delivery problem.
Do you by chance have a inline fuel filter installed?
Have you checked the stock fuel filter in the carb?
I also would not use premium if you have fresh gas already. 87 octane works best.
Sorry for my thick head but what did you mean by "Crack the gas cap" in your previous thread? Did you mean ride with the cap open? or open it to let in air, then close it again?
 

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Discussion Starter #8
Kawasaki recommends replacement of the stock filter @ 2 years. Old filters tend to compress. IMO any air filter is better than stock. I found the Pipercross air filter to flow really well for a foam filter.

No shims or snorkel removal to go along with the slip on?

Also, if your rev limiter is not working, your IC Ignitor is bad.
Correct, that is why I changed the IC Ignitor, but the problem is still there

No shims no snorkel, all stock. Pure stock
 

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Sorry for my thick head but what did you mean by "Crack the gas cap" in your previous thread? Did you mean ride with the cap open? or open it to let in air, then close it again?
If the tank fails to vent properly, it can inhibit fuel flow. Yes, I meant crack the gas cap open to let pressure out then close it again.
 

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Discussion Starter #11
If the tank fails to vent properly, it can inhibit fuel flow. Yes, I meant crack the gas cap open to let pressure out then close it again.
Alright understood, I will give this a shot tomorrow

FYI: My fuel gauge also stopped working completely, it used to show 1/2 tank on a FULL tank of gas, now it just shows empty no matter what. Would this cause an issue with the bike making it think that i am out of gas? causing it to sputter?
 

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....FYI: My fuel gauge also stopped working completely, it used to show 1/2 tank on a FULL tank of gas, now it just shows empty no matter what. Would this cause an issue with the bike making it think that i am out of gas? causing it to sputter?
No, the fuel gauge is just a rudimentary instrument. It's function has nothing to do with anything. There is a green coupling underneath the tank close to the right side that powers the gauge. You can check that, however if the float inside the tank is bad you just replace it.
 

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Discussion Starter #13
No, the fuel gauge is just a rudimentary instrument. It's function has nothing to do with anything. There is a green coupling underneath the tank close to the right side that powers the gauge. You can check that, however if the float inside the tank is bad you just replace it.
Ok great then, I use the tripometer anyway

Still open to suggestions on fixing this bike, and thanks again for all the help. This is frustrating and depressing at the same time. I wish this trouble on no one.
 

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...This problem comes up whenever I try to accelerate really fast. It will get to around 9k RPM and then just completely sputter and bog down, then the power surges up and down. ...

....-The Rev limiter is no longer working (if I WOT in neutral or even first gear i get nothing, it will just dive straight into the red zone [i never hold it there for long, it never did this before])

....-Problem occurs around 9k RPM
Here are a few more things that may be causing your problem.

IC igniter trouble (can cause multiple problems through out rev range. used ones as replacements may have similar or worse results. An aftermarket replacement is a good alternative)
Crankshaft sensor trouble (may explain erratic tach. Also a bad or loose tach connections)
Ignition coil trouble (coil output can degrade at higher rpms)
Fuel level in carburetor float bowl too high or too low (too low of fuel in the bowls can't keep up with WOT demand)

Air cleaner duct poorly sealed
Water or foreign matter in fuel (water is heavier than gas, will settle to bottom of tank and fuel bowls)
Fuel to carburetor insufficient (slides not lifting all the way at WOT)
Fuel tank air vent obstructed
(tank should make a whistle/whining noise due to gas vapor expansion when full of fuel, especially if it's hot)

At 9k the stock Ninja can become really rich. A little extra air helps this area. It is not uncommon for the bike to rich bog and take a little longer getting past this range if already in 6th gear. Going past it in 5th is better. Also keep in mind Altitude, temp, and humidity play large roles affecting engine performance.
 

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Discussion Starter #17
Here are a few more things that may be causing your problem.

IC igniter trouble (can cause multiple problems through out rev range. used ones as replacements may have similar or worse results. An aftermarket replacement is a good alternative)
Crankshaft sensor trouble (may explain erratic tach. Also a bad or loose tach connections)
Ignition coil trouble (coil output can degrade at higher rpms)
Fuel level in carburetor float bowl too high or too low (too low of fuel in the bowls can't keep up with WOT demand)

Air cleaner duct poorly sealed
Water or foreign matter in fuel (water is heavier than gas, will settle to bottom of tank and fuel bowls)
Fuel to carburetor insufficient (slides not lifting all the way at WOT)
Fuel tank air vent obstructed(tank should make a whistle/whining noise due to gas vapor expansion when full of fuel, especially if it's hot)

At 9k the stock Ninja can become really rich. A little extra air helps this area. It is not uncommon for the bike to rich bog and take a little longer getting past this range if already in 6th gear. Going past it in 5th is better. Also keep in mind Altitude, temp, and humidity play large roles affecting engine performance.
IC Igniter: purchased a used one off a 2010 ninja 250, issue is still present at the same RPM as with the old one

Crankshaft sensor: I had a mechanic tell me the same thing, I will take a look into this. However I checked the wiring. Everything seemed nice and tight.

Fuel Tank air vent: Tank whistles/whines/moans normally

Ignition Coil Trouble: I read how ninja 250 ignition coil was solid and rarely goes bad, but who knows. I will get this checked as soon as I can and make sure the voltage going to and coming out of the coil is correct.

Thank you for all help everyone. Again the bike rides normally until 9k RPM or at WOT then the issues start.
 

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Discussion Starter #20
Wow that was funny, but I really hope something this simple IS my issue, if it is I am going to be PISSED. Happily pissed, but angry none the less. This will also go up on the wall of shame
Ladies and gentlemen, I bring you. The source of my pain and suffering
a 3/8'' KOBALT socket........

Yes you heard me, this bad boy was stuck in the bottom vent of my snorkel. After laughing at that Gummy Bear story I thought to myself "what the hell, couldn't hurt to look"

stuck a screw driver up there and this bastard pops out......................

$130 and 13 hours later. for this piece of crap

Took the bike for a run, speed and power is back, and the rev limiter is back as well! Turns out the rev limiter doesn't kick in until the speed/air coming in is high enough. So F me

Thank you Dablue1 and thank you everyone who helped, this is FIXED/resolved!
 

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