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my plug is white eveytiime i check it....wtf

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my bike is a yz400f. i ride about 5 days a week and check/change my plug every second ride. i tried a richer main and no matter how big i go the electrode is still white, the arm is black and if i go real rich then it just gets real sotty. i tried goin richer with the needle as well and it did nothing, its a jd needle, electrode was white and the arm was black. i think the fuel screw is at 1 1/2, didn't touch that yet. the pilot and stuff is still stock. what could i try with those jets. im sure my exhaust isn't leaking. ive got a stock header with a 426 pipe untill my TA slip on comes back. clean filter most of the time. ride between 600 and 1300 feet above sea level. high temps right now are 15 degrees celcius.

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Start with a richer clip position and lean it 1 clip position at a time until it feels right, then check the plug. Your fuel may be burning so clean it's mis-leading.

A likely setting on the YZ400 is-

Stock #45 PJ

1 3/4 turns

Blue needle #4(middle)

#170 MJ

James

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k thanks ill try that out. i never had problems with my jetting at all until i put my ta on and it leaked a bit. my bike is also burning oil now to, kinda don't wanna ride it. what if i went rich everywhere and then went down from there, think thats a good idea??

thanks

shane

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Yes, that is a good plan. Make 1 change at a time and keep a log of what you did with some description of how it ran at each step. This helps when you look back to find the best setting.

James

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alright JD my jetting is as you suggested, 45pj, 1 3/4 turns, blue needle 4th pos. except the 180 main is still in there. the temps right now are between 0 and 15 degrees celcius, winters coming so the tempature will keep going down. i think the bikes running good except there is ALOT of popping when gearing down. i pulled my plug and the electrode is white, the arm is very light brown, and the outside circle is black. it starts first kick alomst all the time if that says anything. this f'in thing is pissin me off, the jettin has been off for a long time according to the plug. how can i tell if its running right with out plug testing. also what are the size increments for the pilot jets. i almost just wanna go like 2 or 3 sizes biger everywhere and make it run crazy rich

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just a newbie searching your forum--but this is what i am told about reading plugs

Center electrode only indicates if plug heat range is correct

top ring of threaded area tells richness or leaness of main jet

good luck

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ok. so how do you tell if the heat range is correct. the book sayds cr8e and thats whats in it. would goin to a cr9e make it a little cooler, also not so lean??

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if the tip of the ground electrode is blue it's too cold (cr9), if the weld point area of the tip to the body is blue it's too hot (cr8)

the plug wont (should not) influence jetting issues.

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I have the same deal with my '04 YZ250F. It SEEMS like half the time it's supposed to be tan the other half it's supposed to be light grey. :thumbsup: I have a #185 main jet and the stock needle in the 5th clip position and I still can't get the frickin' thing to turn tan. It's always light grey. If the last post is correct then I think the #185 main is 1 jet to big so I'm going to put the #182 back in. I'm also going to put the needle clip in the 6th position and see what that does... At least I'm getting a lot of exposure to my carb. :devil:

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At least I'm getting a lot of exposure to my carb. :thumbsup:

The cops chasing you for fogging for misquitoes without a permit? :devil:

man if you havent done any mods to increase air flow a 185 is way too big. A 178 or a 180 is about it for a non modder. try the 3rd or 4th clip position, my 04 liked the 4th.

The grey ceramic could be more from what you are running. What gas do you use?

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If its popping on down changes, its probly still a bit weak.

Have you considered the "sootiness" could be oil burn, possibly stem seals or even rings??

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I have an aftermarket exhaust on it. (Dr. D). It's not burning oil. The insulator is light grey, the first 2 threads are black. I haven't checked for the "combustion ring" like some other posts have advised. I'm going to do that as well. I check FMF's website and they recommended the following jetting for an '04 YZ250F with thier exhaust.

#180 Main

#42 Pilot

4th clip

2 turns out on the fuel screw.

Since Dubach Racing claims that you don't have to change your jetting for thier exhaust I was probably being paranoid about the whole thing after I put it on.

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The dr d pipe, is not a high speed pipe. It's main boost comes down low, and if I remember right it actually signs off faster than the stock pipe. so 185 is definitely too big.

the fmf jetting sounds like a good baseline to start from.

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i changed my 45 pilot to a 48 and went with 1 1/2 turns out with the fuel screw. my main is still 182 and the clip is on the 4th mark on the needle. after a bunch of rides the damn plug is still white on the middle. everywhere else it is black. even the very top on the electrode is white. im tryen to get the it rich enough to foul plugs and go down from there. im thinkin an airleak is leaning it out. where are the most common air leaks on these bikes. im sure the exhaust is tight.

thanks, shane

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