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bike kills plugs still... time to burn it???

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02 yz250

the bike runs awsome and then just dies, has done this for awhile. it can run good for say an hour or 2 and then die. put another plug in and it might last 30 seconds or another hour. and then the plug will not work again. my friend tried it out today with 2006 cdi and coil that i baught off e bay and it ran awsome for 2 hours and died, put a new plug in and ran for 30 seconds and died. he had to get his truck to load put the P O S and go home. any ideas on what else to replace before i buy something else. I am gettin pissed off I already lost out on riding last season.

i put probably a few hundred hours on this bike over the last 3-4 years and then all the sudden it started doing this.

piston has 15 hours on it.

bottem end like 80 hours

jetting is good stock main, 48 pilot, needle second clip

i ride from say 500ft-2500ft above sea level.

i tired an 06 cdi and coil and still does the same thing. should i buy a new stator and throttle position sensor? pretty sure a bike shop wont know what it is and charge me hundreds of $$$$$

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Once had a similar problem on a KX-250. Turns out a small hole on the left lower edge of the reeds was causing too much gas to enter the chamber, consistently fouling my plugs. I'd never really checked them because new rings/pistons/cyl maint. in general didn't require removing the reed block. A thirty dollar set of Boysen resin reeds solved all my problems. Not saying that's what it is, but it's worth a look. Like you, I tried a lot of expensive fixes, and I felt like a real jackass when I found out how simple the problem was.

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reeds are fine, they were missing a chunk of the corner so i put in some good condition stock reeds. i guess i will pull them out again since its been 15 hours since they were put in.

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reeds are fine, they were missing a chunk of the corner so i put in some good condition stock reeds.

That's what I did, too! And they did the same darn thing. So I tried Carbon Tech, and they broke. So did Boysen carbon Pro Series, and FMF. The cheap plastic Boysen's were the only ones that would last at all.

Good luck with it, and if you get too bummed-out with it, pm me and let me know what it would take to buy it. Collecting YZs is a hobby of mine.

:)

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What does the plug look like when you pull it out?

Is it wet?

What type of plug is it?

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i have tried a few plugs br8es br8eg br9es i havn;t riden the bike in 6+ months, my friend said the plug looked fine, wet from trying to jump start it. from what i remember the plug looked fine when i pulled it to swap in a new one.

I really don;t see it being jetting as the first time it happened was out of the blue, then never was the same again. i have had the carb apart to change the pilot to a 48 from a 50. air screw is 1.5 turns out. The bike runs good and then all the sudden it dies. I still think its electrical. probably just going to buy the last few things off e bay.

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I bet the muffler packing is shot...repack it..a temporary fix for the bike would be to run a hotter plug (NGK b7eg) it shouldnt foul anymore plugs or at least not as often but your just masking the real problem...

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Are you sure you're plugs arent fouling from getting crankcase oil in them? That would definitely have the same effects that you're experiencing...

Also how much oil do you have on your air filter? How about coolant getting on the plug?

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If you are getting crank case oil in there, it will smoke like crazy but you won't foul a plug. When my crank case seal went out my bike would smoke you to death, but I never fouled a plug. I would definatly pull your reeds and check them again.

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maybe the powervalve shat the bed... i had something similar with my old yz125 and that was the prob. spent forever trying to chase it down.

or maybe the timing is off.

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This past weekend I had my 02 YZ250 foul a plug just as I was getting ready to line up for a race. Grrr. I pulled out the nearly new Iridium plug and put in just a normal NGK BRE8G plug and it started first kick. That's the second time I've had an Iridium plug fail, but I'm never had issues with the standard plug. Has anyone else had this problem?

Some good suggestions here that have me thinking something else is going on. The timing on fouled plugs is never good.

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