Maintenance & Technical > KX250 / KX125

My bike is a pig. It eats gas and spark plugs.

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mxrider503:
:evil:  My bike eats spark plugs like they are some kind of dirtbike candy. I have to keep a few with me just for a couple hours :( Per my other forum post labeled "My KX250" I thought I had the kinks worked out. I pulled the first plug after an hour maybe two on friday night and it was fouled like a mofo. I turned the airscrew all the way in and brought it out 2 and a half turns plus another 1/8th of a turn because of how fouled the plug was and to my dismay this pig still ate it after about an hour of riding on a fairly rainy next day. The guy who owned the bike before me said he ran race gas because he upped the compression and he ran  br9es ngk plug. However he has yet to supply any specs on compression ratio and other important details (i don't think he knows enough to have done this work) so I ask you dirtbike fanatics to help me in solving this annoying problem. Also the second plug i pulled out looked perfect aside from some excess black all around (spot of tan in the middle). Is this a good plug to run? Will changing the jets in my carb adverslely affect my bike if the compression is infact upped and if so what jets would you suggest and where can I get them quickly? If the bike compression is higher, would running race gas solve this fouling issue? Thanks in advance for your replies.
-brian

John:
Have you seen these informative pictures; http://www.ingfatrygg.se/Spark_plug_diagnostics.html ?

//John

musturbo:
I would also run a compression check.  When my 2-strokes start eating plugs, I usually am due f or a fresh piston.

mxrider503:
good advice john but doesn't really help me other then i can tell you guys that it is a dry carbon buildup possibly from a cold running plug. Any suggestions for a more appropriate plug?

mikesmith:
Since its eating gas and plugs Itd be safe to say its jetted to rich,try one change at a time and take notes on what effect they have.If the compression is to high for the fuel your running itll "ping",and itll ping if your jettings lean,but then you wouldnt be eating gas and fouling plugs,so if its pining try 1/2 race gas and pump gas.Now normally you go by "low range","mid range"and "top end" when it comes to basic jetting,then you can fine tune later.Start with low,does it start ok and run strong up to 1/8 throttle?Being that your out 2 1/2 turns on the air screw you may want to pull the carb and the pilot jet has a # stamped on it,go down one # size try 1 1/2 turns on the air screw and see how it runs.Check the float level,this can really affect mileage (fuel running out the overflow lines) and how the bike runs (especially in the rough).Then for 1/4-3/4 throttle check the clip on the needle,being you seem to be rich try raising the clip a notch.For 1/2 to wide open try a leaner main jet,check the # stamped on the one in the carb and try one # smaller,be carefull testing with a leaner jet (especially the main),dont want pinging/rattlig sound or to seize the bike,itll run hot and can feel like its running out of fuel if to lean (better a little to rich).I normally mail order my parts,but your local dealer will be faster if there in stock,as far as the plug ask for what the bike runs stock and go from there.Remember one change at a time (as time consuming as it may be),take notes for referance,ask here for help,and humidity,altitude,and temperature all effect jetting!A manual is worth the money or even the owners book can help,but dont be scared to ask someone here for help.

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