SX 250 2014 Revs without throttle

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1/16/2018 9:53 AM
Edited Date/Time: 1/16/2018 10:09 AM


last time i rode my 2014 ktm 250sx it revs over max without throttle. This first happens in the Air on a big jump.
The bike revs higher than full throttle and the kill switch wont work. After that i checked everything, carb, throttle cable, fuel hose, connections between cylinder and carb.
Everything looks perfect. I testet the bike on the stand more than five mins. Everything perfect.
Then i ride again and after 200 meters, one second after landing a small jump it happens again. Instant rev to the moon, faster as a full throttle rev, really instant... (my first backflip on a bike after 12 years riding^^).

At home i checked everything again, everything perfect. And i cant repeat this self rev....

I read much about air leaks, but if there is an air leak, why it revs not all the time like this? And with an air leak the rev normally goes high without power i think. But my bike has max power while it revs itself this two times...

Hope you can help me to find the issue. Scary to ride this bike again without finding the reason. Dont want a second hospital visit because my bike is silly....

Sorry for my bad english, greedings from Germany ;P


1/16/2018 11:03 AM

Are you positive that the cable housing isn't coming out of the top of the carb and getting hung up? Like under the rubber boot area. Also, I thought there was a throttle housing recall around that time. I never had an issue with my 2013 250sx but have heard of this a few times in the past. Good luck!


1/16/2018 11:15 AM

Check for air leaks and check the float height. Also make sure the throttle cable is not binding.

Paw Paw


1/16/2018 12:02 PM

Thx for your answers, i bought my bike 04.2014. No recall for this „last“ 2014 models. (checked my bike with the ident nr on ktm website).

Iam 99% sure its not the throttle cable or housing, Looked there while the bile revs high first time and everything was ok. But i will check it again.

I will check float height and for air leaks tomorrow, can you explain me why an air leak should be inconstat like the failure on my bike? And why my bike got full horsepower if its a lean condition because an air leak?


1/16/2018 12:39 PM

Back flip? Ok, it may be 1. your spoke wraps are on wrong2. your metal milisha stickers are upside down or 3. you choose the wrong color of flat black when painting the plastic.......


1/16/2018 2:28 PM

Spray starting ether or carb clean around the reed block. If the RPMs increase, it’s sucking air somewhere. Not sure if it’s the same on the 250, but my 150 had some sealing issues with the stock reed cage. Also, with the bike off, take the intake boot off and hold the throttle wide open and watch the slide return. Should be rapid and totally smooth.


If you're not mixing gas, you're not haulin ass.

1/16/2018 2:31 PM

There was a recall on the wheel and bushing inside the throttle housing. I had the recall work done by a dealer after the throttle sticking wide open on me twice, didn’t fix anything still stuck on me. Replaced the wheel and bushing with the one from my ‘06 KX250 and problem solved. Try replacing those parts. Photo


1/16/2018 4:15 PM

Check your throttle housing for tightness. You may somehow be jamming the grip wide open when you land from jumps and if your housing moves so the throttle tube catches on the bar end, it gets stuck that way. A long shot, I know, but something similar happened to me once.
You should be able to feel a tiny bit of wiggle left/right with your throttle tube so you know it isn't binding on the bar end.


Braaapin' aint easy.

1/17/2018 7:47 AM

ok disassembled my bike again, i feel the wiggle, checked throttle housing, checked throttle cable, looked for air leaks (with carb cleaner), checked everything in the carb, checked reeds, checked piston and cylinder.... everything looks like new.

Is there anything else i can check? Or do you think iam safe with new seals? Or better a complete new carb(but everything in there is fine...)

Scary to ride without finding the reason...


1/17/2018 3:54 PM

Look into getting a motion pro throttle cable. The stock cable is junk


1/17/2018 3:57 PM
Edited Date/Time: 1/17/2018 4:00 PM

Left side crank seal behind the flywheel will make it run lean and rev to the moon. Happened to my bike and the killswitch will not stop it. I had to put it in gear, hold the rear brake, and let the clutch out before it finally stopped. I held the killswitch for over a minute. It sounded weird too not like It does when it revs normally. This would happen when the bike was low on fuel


1/18/2018 3:52 AM

Hi i had a leaking power valve seal that made my bike rev to the moon.

i replaced the power valve seals, and the O-rings on the boost port power valve. Also recommend using gasket seal on the left side powervalve cover gasket.


1/18/2018 6:53 PM

And so the circle of questions go......

Ask the resident KTM/Husky expert, his name is Tamir. He will thank you.


much ty. How to spot a paid forum poster/artificial forum traffic producer (see list of actions/phrases below):

Copius pattern amounts of phrases like “Anyone have”..., “Anybody know?”.... and their variations.

Any help is appreciated!
Thanks in advance!