KX Riders
Maintenance & Technical => KX250 / KX125 => Topic started by: Caddy 16v on June 12, 2011, 04:02:43 AM
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Hi,
I have a new/ old problem since my bike ('91 KX250) has now successfully killed two of my sparkplugs after around 1h of ride time! I can't really go anywhere without having to worry that I'll die and I'll be pushing for a long time.
The thing is it gets gradually worse, with a new plug it runs crisp and then starts to bog every now and then until it finally has no more spark. When I test the plugs on another bike they are still dead.
I have a suspicion but want to hear your suggestions as well: I'm running a '91 igniter and ignition coil but the bottom end is from a '89 so there is a '89 stator in there and I suspect that is not playing along as it should and kills the plugs!? :?
Thanks in advance.
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What color is the plug after you remove it? Black/wet would mean your jetting is to rich.
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X2 on jetting, spark pretty well works or it doesnt.
Also if youre running a really cold plug & lugging around that would exacerbate a jetting issue.
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I was running a bit rich (dark black color) for a while and the plug was wet at times but yesterday I changed it and it was dry after that, might have been already gone too far? First it was a NGK B9ES and then a BR9EIX iridium plug.
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If I'm trail riding where there is alot of lugging & not alot of winding it out I'll run a br7 generally I run a br8 but I do jet a bit rich for my elevation. You do need to pull the carb & check the jet size though. Baseline with a kehin 55 pilot, 170 main, middle clip, with no regard to your elevation temp etc...
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I think a hotter spark plug might work I should give it a try. Thats how the plug looked like when it died:
(http://i593.photobucket.com/albums/tt13/caddy_16v/Motocross/DSCN0657.jpg)
and the previous one:
(http://i593.photobucket.com/albums/tt13/caddy_16v/Motocross/DSCN0658.jpg)
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Jetting
Someone else wanna chime in here
On the plug I'm at 5500' plus all the time so I dont know that it is for everyone as I run a bit rich, rather safe than sorry but , 15-20 hours is a plugs life in my oppinion not an 1hr. If I do run a quality synth blend oil like klotz though they last even longer
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Plug looks soaked, too much fuel
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Check the stator and coil cold, put a new plug in untill failure and recheck stator and coil with ohm meter. If its getting progressively worse the electrics are probably failing under heat sooner aand sooner. If it were jetting, I believe it would be problem from the start. The plug will appear soaked if not enough voltage is shooting through.
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Check the stator and coil cold, put a new plug in untill failure and recheck stator and coil with ohm meter. If its getting progressively worse the electrics are probably failing under heat sooner aand sooner. If it were jetting, I believe it would be problem from the start. The plug will appear soaked if not enough voltage is shooting through.
good to know. would make sense to start at the electrical
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some one once told me that if your spark is blue its good af its got any white in the spark its a gas soked plug time for a new one and if its red spark its your coil that what i know and thats the colour of the spark not the spark plug
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Thanks, I seem to remember that the colour of the spark is blueish, I got a BR8ES today so hope that will help. Right now I'm at a 168 main with the needle on the first clip from above since the third and second clip totally soaked it. I'll have to check what size pilot is in there though. I think I'll still have a 165 main hanging around somewhere.
If it should still die early I'll try a spare coil and ignition.
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So it had a 55 pilot jet in there, I had a 52 laying around so I went for that one, it seems to run a bit better now and the color changed to a dark brown/ blackish. It seems like a 50 pilot jet was the smallest available for that year, so could I even go smaller since they make them smaller??
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I think a hotter spark plug might work I should give it a try. Thats how the plug looked like when it died:
(http://i593.photobucket.com/albums/tt13/caddy_16v/Motocross/DSCN0657.jpg)
and the previous one:
(http://i593.photobucket.com/albums/tt13/caddy_16v/Motocross/DSCN0658.jpg)
Wow.. You have longer fingernails than my wife.. :|
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lol I had to cut them later, they were annoying :mrgreen:
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The blue spark sounds like a good tip havent heard that before.
I dont know that I'd go leaner on the pilot though you should be able to tell by the air screw where your at, the sweet spot should be 1-2 turns out more than that means larger on the pilot less means smaller if I remeber correctly
Could be ignition related my only ignition problems have been cdi related & from my expierience they just die. Maybe corroded stator not giving full current?
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Picked up a 45, 48 and 50 pilot jet and a 152 and 160 main jet. I'll start with the highest number and see how it does, don't think I'll use the 152 though.
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Alright so I had some time to switch the jets and went with a 48 pilot and a 160 main jet, needle first clip and 1.5 turns out (fastest idle) on the air screw and WOW did that ever wake the bike up, it revs fantastic now and hits hard!! :-o
I think my spark plug picture is way better now, too, but you guys be the judge!?
(http://i593.photobucket.com/albums/tt13/caddy_16v/Motocross/DSCN0688.jpg)
(http://i593.photobucket.com/albums/tt13/caddy_16v/Motocross/DSCN0692.jpg)
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You really didnt need to trim the nail, i think shavings way over rated too..
Here's some plug pics, but I really want to find plug chop info/photos as that is the true way to accurately do your jetting, it sounds quite lean to me where your at, which will melt motors
http://www.dansmc.com/spark_plugs/spark_plugs_catalog.html
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Too funny that a bunch of dudes on a hot rod dirtbike site would point out somebodies long fingernails :lol: :lol: :lol: :lol:
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heres another good article on jetting but still no plug chop photo with the clearly ilustrated halo
http://www.thumpertalk.com/forum/archive/index.php/t-412662.html
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Finally found the halo, every 2 stroke site should have these stickied & refer all jetting questions to the halo
http://www.blasterforum.com/do-yourself-20/how-plug-chop-38674/
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Thanks for researching those threads, already read through the plug chop...I'd have to find a long straight first in order to do one. Also I might move the needle down a clip but it might just start fouling again, from what I've found on Thumpertalk almost everyone is running a way smaller pilot (38-42 etc.) and main jet as well, so I might even be on the richer side still.
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I run 11000 feet ,litterally, with 165 & 55, bit rich but if you stay riding it, like my grandma who drove 105 on the freeway,it'll stay clean. Not to be a rude ass but if everything else is good open it up it'll blow it out & clean the plug. It really sounds a bit lean to me reeds & a pipe go a long way. I really aint trying to be rude just know how it works for me & to see a hang up like you got it says dude is scared like i was for the first 2 months after that you go hey this really aint gonna kill me me I want MORE you'll quit fouling & start reading perfomance mod posts