Question about 2008 KTM 250 SX

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New spark plugs last 10-15 minutes of riding

2008 model KTM 250 SX from the day of the purchess we having problems with spark plugs. After worming up the bike 10-15 minutes of riding if we go to have a rest, we switch off the engine. When we restart its start with no problem but after a little idoling we wont to go for next ride the bike just loose the power and die. Only way to restart the bike is change the spark plugs for new one. We believe so that is the big problem with something we canot explain. The enjoyment off the riding the bike is spoiled by this incident which occure on regular basses. I had before 2000 model 250 SX where i didnt experience any of this problems. The carburetor setting 1; 42; N1EI; 3; 158 . Please help me solve this problem becouse I am loosing interest of riding this bike.
Thank you
Regards Martin

Posted by on

  • 250sx Mar 07, 2009


    I think I have the same problem as Martin, I have just bought a 2006 250 SX, the guy who I bought this from was running it way too rich, 32:1, and the pipe and silencer was pretty oiled up.. I have cleaned it up a bit( cleaned out the carburetor,put in a new spark splug, opened up the power valves and cleaned them)

    The next time I rode, 3 laps around the track and the bike just died.. It felt like fuel starvation so I took the carb apart and and everything looked fine and plenty fuel was getting through. I took the spark plug out and it was totally dry burning light brown.

    I am about to go buy a new plug now and see if that helps, I will check the plug cap too but other than that I don't know what could be the problem with this bike!!

    I think Benimur is talking about a self autolube tank, the KTM you have to mix the fuel yourself so it does not have an oil injector.

    If anyone who has had this problem or knows what could be the cause it would be greatly appreciated for your advise.


  • paul
    paul Dec 07, 2013

    what 2 stroke oil make are you using ? only use race oil as it is a race tuned motor ! you got the correct heat range plug ? sounds like plug could do with a hotter range if everything else fails ! check pluggap is correct ! let me have your feed back and if i can help more ! P...



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I also have a 08 250sx . ive been having the same problem recently, always on idle or when reving to take off withing 15 seconds of starting. went one size down on idle jet and 1/2 out with air at 158 main 40 idle 1 1/2 turns out,stock needle 3rd groove.... thought it was solved but eventually blew another plug at about 1/4 throttle a min or two after starting. but it ran better at idle and off idle. sounded better too.
think ill go one groove on the needle next and see what happens.
its definitely a jetting issue!!!

Posted on May 19, 2010

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Hi had same problem changed to a ngk 8 spark plug run fine since

Posted on May 19, 2009

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Hi and welcome to FixYa,

Offhand, the only factor to be checked that could foul a sparkplug for your bike would be the 2T oil injector/pump. There is too much 2T oil going to the combustion chamber. Either the injector would require restricting or for some reason, there is also 2T oil in the fuel tank (pre-mix).

Good luck and Thank you for using FixYa. Happy Holidays.

Posted on Dec 07, 2008

  • Louie  Role
    Louie Role Dec 14, 2008

    May I inquire as to why the posted solution was rated inappropriate?


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