Question about 2003 kawasaki KX 250

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Kawasaki kx 250 fouls spark plug in 30 minutes

I just bought a 2001 kx 250 for 14 year old son. It was used for motorcross by an adult. This is my son's first motorcycle and after riding the bike on day one it cut out and we could not restart. Pulled spark plug and it was fouled. Put in new plug, cranked right up, ran for 30 minutes and cut out. Pulled plug and it also was fouled. Put in new plug and won't start at all. I'm assuming this bike is set up to run hard and we are stalling and putting around in the backyard at low rpm's. There is no splooge coming out of tail pipe. The plug is black and dry not oily. The new plugs are autolite (had to order NGK's they'll be in tomorrow). Will the NGK iradium plug fix the problem or does the bike need to be retuned for a novice rider?
Thanks in advance for any help.
Pete

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  • 4 more comments 
  • petekulenek Dec 08, 2008

    Thanks drumbanger,
    I'm using fuel/oil mix from manual of 32:1. Do you think I should maybe try 50:1 before I start tearing the bike down?
    Pete


  • petekulenek Dec 09, 2008

    Thanks rselvy,
    I changed the fuel/oil mix to 40:1 and put in a NGK BR8EIX spark plug which got it started and my son was able to ride for a couple of hours. I haven't checked the condition of the plug yet. I also ordered a NGK BR7EIX just in case.
    Thanks again for everyone's help,
    Pete


  • Anonymous Dec 27, 2008

    i want some of thhat asatchs bi

  • Anonymous Apr 06, 2009

    i have a kx 125 2002 model.Spark plug keeps gettin fouled up , using a ratio 25:1 is that the problem.Not riding it real hard yet as i am only learning

  • Toyota Ed May 11, 2010

    I too agree with Rselvy.

    The solution from Drumbanger is not an appropriate solution.

  • Anonymous Mar 16, 2014

    2001 dyna low rider,wont start and is back firing through the carb,it was running but back firing around 3000 rpm,rebuilt the carb and changed the intake gaskets,it ran for about 10 minutes like new then cut off,wont start now and is back firing through the carb,HELP

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You definitely need to change the oil mixture to at least 40:1, use a good grade of 2 stroke oil. You do NOT need to return the bike. I'd highly recommend using an NGK B7EV spark plug. A hotter plug will stop the premature fouling. I would not recommend you decrease the oil to 50:1 because you are essentially robbing the engine from adequate oiling for the piston, KIPPS valves and the bearings. The hotter plug will make a huge difference but remember if he gets to the point where he is able to ride the bike to it's potential he will need to run the cooler plug, B8EV or B9EV. You can also use a cheaper plug in the same heat range, B7ES or B8ES. Those plugs should cost about $1.25 ea. and are an affordable cost of running the bike. It's not uncommon to replace a spark plug frequently, it's the nature of the 2 stroke engine.

Posted on Dec 08, 2008

  • craig Oct 04, 2011

    kx 250 / 1999 /sparkpulg is br8eg

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Here to tell you that although all of the above answers are mostly opinions and best guesses that your son would have no problems with his oil mixture being at 50:1, here's a quick lesson. It sounds like your son is new to this bike and not quite twisting the throttle all the way just yet, without knowing what jets are in the carb its kind of hard to diagnose and there are other factors such as elevation, weather, temperatures, and overall wear on the motor. When you bought this bike did you check the compression? A worn piston & rings can drastically damper your running and starting, does it seem to sound like something is rattling around while at idle? Another common mistake made is the oiling of the air filter, if to much oil is applied on the filter it will cause a rich running condition almost as if there was a second choke on carb. Bottom line, make sure motor is sound and filter is installed properly, stay here with a BR8ES and for now go with 50:1 with a good full or semi synthetic oil, and to the other oil experts just remember that in a combustion chamber there's this event that happens called "burn time" that's how long the explosion lasts inside your cylinder, now what burns faster, oil or gasoline? That's right gasoline, when mixed together it can be controlled thus meaning the more oil, the longer the burn which equals to higher temperatures resulting in detonation and then catostrophic engine failure , changing a plug to a hotter one will not solve this problem.

Posted on Oct 22, 2012

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I agree with rselvy

40 to 1 the most you would ever run a dirt bike. Ignore dumbanger solution or you may sieze the engine... 50:1 is way to little oil for this type of motor!!

regards
robotek

Posted on Dec 08, 2008

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I am also having the same problem with my '06 kx250. I actually changed my riding style at the track to try to keep from fouling plugs, almost never going above 2nd gear unless I have to, whichreally sucks... just to keep the rpms super crazy high. I was running 32:1. After asking around, I think I too will start running 3.5 oz oil/gallon of fuel instead of 4. Also considering changing from klotz to something else... any suggestions?

Posted on May 01, 2012

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Just to let you know i race kx250 do not go any lower than 40:1 mix the plug your now ridding with is good same one I use and we race pro supercross.Big bike for 14 year old if you ever need parts try ebay.com great place for parts

Posted on Apr 22, 2009

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Your gas flow jets may need cleaned or or air intak in carb needs adjusting (sounds like its burning too much fule ands needs more air in mix,also watch your gas oil mix!

Posted on Dec 08, 2008

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