Which Spark Plug to Use?

Greetings from sandy, muddy, cloudy, sunny Michigan. I searched the archives for plug suggestions and came up short. I just bought a replacement(NGK CR8E) for my fouled out stock Denso plug and was hoping to get some feedback on plug choices. I heard that NGK's w/ ***EG are supposed to be platinum, but I couldn't get ahold of one. What's the scoop, oh knowledgeable thumpers?



I am going through the same thing you are (looking for the best plug). I have a buddy here on TT that I race with who has the 99 YZ400F and the 01 YZ250F. Based on his experience the splitfire 430B??? works for him. I am going to check the numbers again with him then order one for my WR250F to try.

hope this is helpful,




2001 WR250F - Snorkle out, t-stop cut, grey wire mod, YZ timed, DR.D Pipe, Ty Davis/IMS seat and tank, handlebar hot start, panoram computer, Mich S-12 Rear/ Mich starcross MS2 front, Ty Davis rad supports, Scotts Damper and triple clamp w/ Protaper bars, stock jetting, fuel screw 1.75 out, that's about it...

How often should you change them. I got ovet 1000mi on my 01 426 and it still runs like a champ.


I went to my dealer the other day and asked for replacement plug for 98 WR and he gave me NGK CR8EVX. I figured it was what came with bike since I just got it but when I pulled the plug and looked in my shop manual it has the NGK CR8E. The box for the CR8EVX says Platimum on it. I wasn't sure if I should use the platinum one or not. Is there a difference? Will the bike run hotter? Any suggestions would be helpful.



I live in Michigan also. I understand about the weather beleive me. I own a WR426, and had no problems with plugs as of yet. However, did you change anything in the carb? Just thought I would ask.


My 2 cents:I have tried both the NGK CR8E & the CR8EIX -platinum plugs. I found the CR8E works everywhere - meaning all altitudes. The Platinum CR8EIX worked great in one location/altitude but fouled out in lower Altitudes during kickstart (all over 1 weekend)The CR8E was not affected. The difference in altitude was minimal all in NGeorgia area. I was not able to tell any real difference in performance although technically the platinum should be a better plug. It is around 4-6bucks also.

I have never used any other brand.

Sorry the CR8EIX is not Platinum, it is Iridium


I'm all stock except the airbox lid, throttle stop, and grey wire. Everything is running flawless right now. I'm enjoying it while I can.

Originally posted by *mike68*:

How often should you change them. I got ovet 1000mi on my 01 426 and it still runs like a champ.

I have heard that the electrode can get fatigued and break off after time. What I heard was to change them at least every 1000 miles.

- Sean

I had a cr8e in for two years.(2200 miles)

then I cut the grey wire and the plug fouled 20 miles later(changed it on a mosquito infested trail).

should have done it sooner :)

I'm pretty sure there is no connection.

I'm sure my plug was just too old.

I am now replaceing my balencer drive gear straight key.(mine is all smashed up)

hope it is the source of my engine rattle.

finally a place to get great info.

Big thanks to everyone at thumpertalk :D :D :D

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