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Misfire at full throttle

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Hello people.

My kx250 2008 has a misfire at wide open throttle.

Will

Not rev cleanly through at all. Sounds like its overly rich so I altered jetting to suit. Same problem, reeds are new to.

Does anyone know if the cdi unit or any other electrical item are prone to failure?

I'm going to check coil out put when I get time to see if spark is wasting somewhere? Maybe to earth.

Regards

Karen

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First I'll start off to those who question an 08.... SHE'S IN THE U.K. Lucky lady. LOL

As for th issue, Start with:

the sparkplug, if you haven't changed it out yet. It may have a small crack in the ceramic.

v

If new plug...

v

Check wire and plug end. They actually thread in the wire.

v

check stator assembly. you'll have to remove flywheel to make sure there's no small broken wires in the winding or possibly damaged/missing woodruff key (keyway).

v

coil - use a multimeter to check coil resistance.

v

CDI- possibly. There's a way to check them but I can't remember, I just look it up.

v

Then comes mechanical:

Last topend rebuild???

KIPS working properly

Edited by SAPPERS

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First I'll start off to those who question an 08.... HE'S IN THE U.K. Lucky bastard. LOL

As for th issue, Start with:

the sparkplug, if you haven't changed it out yet. It may have a small crack in the ceramic.

v

If new plug...

v

Check wire and plug end. They actually thread in the wire.

v

check stator assembly. you'll have to remove flywheel to make sure there's no small broken wires in the winding or possibly damaged/missing woodruff key (keyway).

v

coil - use a multimeter to check coil resistance.

v

CDI- possibly. There's a way to check them but I can't remember, I just look it up.

v

Then comes mechanical:

Last topend rebuild???

KIPS working properly

He he I'm a woman in the uk not a man. Lol:-)

I have just finished rebuild of engine, all bearings replaced, 3rd gear output shaft replaced, all seals and crank. The bike seized 3rd gear the first time I rode it.

The engine did this exact same misfire before it died so I was hoping that after all the work I've just done the misfire would be gone. The bearing seals were leaking so I was hoping an air leak was its problem.

Turns out it wasn't! The Misfire is still there at full chat which takes me down maybe the electrical route as problem is only under load.

Starting to annoy me to be fair. Have spent to much already on it and haven't ridden it enough.

Regards

Karen x

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When did the kx 250 stop in America ?

07

and previous post fixed.

We'll try to help you. Chokey or Jeekinz may have some insight on this.

Edited by SAPPERS

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The plug is a new ngk. Can't see anything obvious but I had a similar problem with one of my speedway bikes. Turned out to be the kill switch shorting out at a certain handlebar vibration.

It's a weird misfire kind of like a bwaaaaaaarrrrrp

Instead of a braaaap if that makes sense?

Can't believe you guys lost the 2 stroke at 07. ;-(

Is that cos of all the enviro nutters moaning?

Will check other stuff Tomoz and keep you informed. Was hoping that someone had had a similar problem.

I'm racing on Saturday .

Regards

Karen

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Sometimes, if it acts overly rich, it is - but not from jetting. After checking out ignition issues, you may want to swap carbs with someone and see if that fixes it. I had purchased a KDX220 that misfired (acted like rich) on top and would not rev out cleanly (sounds a lot like yours)- it turned out to be a bad carb...sometimes an air passage gets blocked internally - rare but it does happen. (I've read of others with that issue too - a bit of carb metal lodges internally-impossible to find). I had completely torn the carb down, including the jet block, ran wires through everything, compressed air, etc. As soon as I swapped out the carb it ran perfectly.

The previous owner had gone to great expense trying to lean out the carb, but nothing worked. The piston and head looked brand new, shiney and clean from too much fuel. Try running it out of gas and see if it revs up higher before it dies as it runs out of fuel.

Edited by SPUTTER

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Think i may have Found problem! Cdi unit is full of sand and heavy salt Water corrosion as a result of the Weston beach race in 2009.

Looks expensive to me!

I think I can safely say that I brought a turd.

Suspension problems, transmission seizure and now this. ;-(

Should have brought another ktm and stuck with what I knew.

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Think i may have Found problem! Cdi unit is full of sand and heavy salt Water corrosion as a result of the Weston beach race in 2009.

Looks expensive to me!

I think I can safely say that I brought a turd.

Suspension problems, transmission seizure and now this. ;-(

Should have brought another ktm and stuck with what I knew.

Good god my friends 300EXC just lost a CDI too! We need a CDI appreciation week. So they dont keep killing themselves left and right.

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Good god my friends 300EXC just lost a CDI too! We need a CDI appreciation week. So they dont keep killing themselves left and right.

Bring back contact points! At least you could work on them.

Unit is about 360 quid. Could waste the whole season trying to find a secondhand one. Kawasaki have me over a barrell!!

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Interesting topic. My 07 has the same problem. Its done it since new and only when revved out fully. I dont notice it when trail riding but when the section opens up it brakes up up top. Most noticeabe in 4thand 5th gears. Cases were split recently to replace both leaking crank seals, no signs of corrosion on the ignition components, fresh top end, 110 octane race fuel. Its not ridden much and will look into it soon.

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Does anybody know if there's an alternative avaible for cdi unit like microtec and magneti marelli? Something's that's Like a power commander style thing? Or just a generic replacement.

In anger this evening sawed 6 inches off the crap fmf turbine core pipe that was on there and removed the spark arrestor cos I didn't like that stupid big pipe anyway.

Looks like a shorty now. Much better for anger management

Regards

Karen

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Does anybody know if there's an alternative avaible for cdi unit like microtec and magneti marelli? Something's that's Like a power commander style thing? Or just a generic replacement.

In anger this evening sawed 6 inches off the crap fmf turbine core pipe that was on there and removed the spark arrestor cos I didn't like that stupid big pipe anyway.

Looks like a shorty now. Much better for anger management

Regards

Karen

Vortex makes a CDI for the 05+ kx250 but I have never tried one or heard from someone that has.

I think I have the same problem as you as well does it sound like it's popping back into the air box? Can you feel the sides of the air box move with your legs when it does? I've gone through my whole bike tying to track this down, with no luck. I'm at my last hope now I talked to a kawi tech and he said to look and see if the carb vent lines are clogged up. I'm in the process of replacing all the vent lines now, *fingers crossed*

Oh and what pipe are you running? I had thought that could be the issue but a switch back to the OEM pipe didn't change anything at least for me... :thumbsup:

http://www.vortexcdi.com/model_product.php?product=1&model=62&mp_id=983

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Go over the entire bike and check all the electrical connections. My 98yz250 did something like that, turned out I had a loose connection to the CDI. Fixed that and she ran like a top.

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Vortex makes a CDI for the 05+ kx250 but I have never tried one or heard from someone that has.

I think I have the same problem as you as well does it sound like it's popping back into the air box? Can you feel the sides of the air box move with your legs when it does? I've gone through my whole bike tying to track this down, with no luck. I'm at my last hope now I talked to a kawi tech and he said to look and see if the carb vent lines are clogged up. I'm in the process of replacing all the vent lines now, *fingers crossed*

Oh and what pipe are you running? I had thought that could be the issue but a switch back to the OEM pipe didn't change anything at least for me... :thumbsup:

http://www.vortexcdi.com/model_product.php?product=1&model=62&mp_id=983

Standard front pipe and fmf rear (now modified)

I have tried stock pipes, tried air vents, swapped the carb with another and no difference then I found my cdi eating itself alive.

Yeah the air box sides suck In and kinda like a weird harmonic pressure vibration, like when you have one car window open in the rear of your car and at speed the pressure can't balance out so gives you that weird sensation in your ears. If that makes sense?

Good luck with it!

Karen

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I need a woman that rides and works on bikes...lol stick to kawasaki. Green looks better on women than orange..:thumbsup:

Lol :-)

Won't be going back to ktm as the colour does suck! Even with black plastic kit!

Will persevere with kwakka

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Think i may have Found problem! Cdi unit is full of sand and heavy salt Water corrosion as a result of the Weston beach race in 2009.

Looks expensive to me!

I think I can safely say that I brought a turd.

Suspension problems, transmission seizure and now this. ;-(

Should have brought another ktm and stuck with what I knew.

hi,

 

how did you come up with that, i mean the cdi failure,  my kx250 does the same thing,  ive changed jetting up and down  enough, changed petals, piston and crank seals  and the bike just keeps doing the same, it only happens on the track when revving out of turns,    how can i check if its my cdi failing?

 

did you fix it?  or just gave up with the cdi expense?

 

thanks  hope your still here!

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