i know its super hard to see.but from the bottom it goes grey to a small strip of white to gray then light tan to a dark brown on top..basically i am lean at WOT RIGHT?
The spark plug CANNOT tell you if your engine is rich or lean. A spark plug cannot tell you if your engine is developing max power. The only thing that a spark plug can tell you is the temperature that the spark plug is operating at.
A spark plug cannot tell you the air fuel ratio, neither can an O2 sensor tell you A/F ratio of what JUST HAPPENED IN THE COMBUSTION CHAMBER IN A TWO STROKE ENGINE. There is a very popular dyno manufacture that is trying to train new dyno operators on how to use an 02 sensors for tuning two strokes. A two stroke will fool an 02 sensor because of the short circuiting and the over scavenged mixture that passes through a two stroke engine and escapes the combustion process.
I can raise the coolant temperature (spark plug base temperature) and guys who read plugs for mixture will say it is leaner. I can lower the coolant temp and spark plug reading guys will say it is rich. I can run the same plug and jetting an make 2 seconds dyno runs and guys will say it is rich. I can run the same plug and jetting and make a 15 to 20 second dyno run and guys will say it is lean. I can run one heat range colder than what the engine needs for the load the engine is experiencing and guys will say it is rich. Again the spark plug can only show you the temperature that it HAS reached and how much time the spark plug has on it since it was installed.
The spark plug pictured above has had two of the key areas removed that will give a vague indication of the combustion temperatures the spark plug has been exposed to. The tip of the above spark plug pictured above is not operating at a high enough temperature to keep the deposits burned off. It could be the result of too cold of a heat range for the length of time the throttle is held wide open. The dark plug tip could be the result of head temperatures that are too cold for the heat range of the plug. It could be the result of running around a few minutes at partial throttle since the engine has had a few wide open passes through the gears. It could be rich but you will know that it is rich enough to darken the tip because it will be misfiring. If the tip is dark on only one side, the dark side of the spark plug will face the carb carburetor side of the engine when installed.
Peak combustion temperatures are in the 3000 to 5000 deg range in a two stroke engine. A spark plug will usually cause pre ignition when any part of it reaches temperatures around 1400 deg F or higher.
A spark plug can help reveal if mild detonation has been occurring. Microscopic pepper like specks will accumulate on the porcelain cone that surrounds the center electrode. A magnifying glass must be used to see these small specks. Severe detonation is easy to spot because the spark plug may have the ground strap burned off or the porcelain cone will be covered with molten aluminum or you engine just quit because it has a hole in the center of the piston or the piston seized.
It is unfortunate that there are a lot of guys that are trying to read spark plug readings to tune their engines for max performance based upon the misinformation than has become rampant based upon spark plug dissection or mutilation.
Tuning an engine is not rocket science. Tune it so that it runs right and monitor the spark plug for indication of detonation. If you make a jetting change and cannot feel a difference or see a difference on the dyno or a drag race, you are at max power as long as the engine is not experiencing ANY detonation. Most engine will have about a one to three jet spread where the engine makes the same peak power. Poorly developed engines will have a much narrower range of jets where max power occurs and where the engine burns up or the power suffers because it is rich.
