Need an opinion about my color plug

[Buffalo400]

The color of my spark plug is yellow like a " light gold " (not brown) after a plug test (WOT) with a 155 main jet on my 400ex. Yes, it is too lean. Does a 158, 160 or 165 will be fine?

My mod are grinded header, slip-on fmf, uni filter, no lid, 402cc piston... I run at 1200 feets and 15 degré celcius...

Thanks

well I cant answer you question, but I can tell you that you want the burn mark on the plug to be one the bend. ( where the tab starts to bend and connect to the body of the plug) or maby just a little bit more ( more dark on the flat part)

hope that makes secnce to ya, prolly already knew that tho.

I would guesss at 160???

[2004exrider]

dark grey-light brown: perfect
white: lean
dark brown-black:rich

so i would say its perfect!

[prepracing]

as long as its not popping and backfiring, running a little lean will not hurt anything, a little on the lean side will give better performance

[2001300exguy]

http://www.atvriders.com/articles/sparkplug.html