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Odd spark plug color.

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I was recently fouling plugs within a few minutes after starting my 01 YZ125 so I started making some air screw adjustments this weekend. At about 2 turns out the bike was pulling pretty hard thru out the band with a barely noticeable bog when twisting the throttle and, didn't foul. I pulled the plug and this is what it looked like (sorry, no pics). Looking straight down into the bottom of the plug imagine looking at a circle then draw a line thru the middle. Exactly 1 half of the plug was dry and black, the other half was dry and white. In other words, half of the plug had a lean color, the other half rich. Anyone ever see that color pattern before or have any ideas what would cause it?

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sounds like you need to give it a good 30 hard ride to see what the plug looks like. If you are getting good throttle response with a little bog off bottom then more than likely your about spot on.

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I was recently fouling plugs within a few minutes after starting my 01 YZ125 so I started making some air screw adjustments this weekend. At about 2 turns out the bike was pulling pretty hard thru out the band with a barely noticeable bog when twisting the throttle and, didn't foul. I pulled the plug and this is what it looked like (sorry, no pics). Looking straight down into the bottom of the plug imagine looking at a circle then draw a line thru the middle. Exactly 1 half of the plug was dry and black, the other half was dry and white. In other words, half of the plug had a lean color, the other half rich. Anyone ever see that color pattern before or have any ideas what would cause it?

bet you are looking at the difference of the exhaust side and intake side

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I had thought about the color difference being caused by intake and exhaust side but wasn't sure if that was possible. I'm rather inexperienced with the 2 strokes. Anyway, I put in a new plug and rode for about 30 minutes in the woods. Pulled the plug and it was a chocolate color, thought I could live with that. Let it set for about 30 minutes, started it and warmed for a few minutes then rode about 100 feet from the shop and it fouled.

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