Your first and main concern with mixture is with wide open throttle for this is what burns up an engine by overheating it. Unless you have the equipment to check the A/F mixture the only accurate way to check is the WOT run. You will need an old colored plug and a strait run of 900-1200 feet,(phone poles are 300' apart). First you will loosen your plug and then lightly snug it down, this is so that when you remove it to read it is not so tight that you pull threads out with the plug. Bring your plug wrench with you. With engine at operating temp from a dead stop accelerate to full throttle for the 900'-1200' run never letting off full throttle. Once you reach the 900'-1200' mark with your throttle still in full open turn the engine off. Only after engine stops do you lift off of full throttle. This makes sure your plug will only read at full throttle and not idle circuit. Pull your plug and read by inspecting for color around the rim right above the threads, the ground strap and porcelain. If proper it should read anywhere from a light tan to a medium brown. You should also make sure your compression is good, a worn or too tight valve setting can give you a lean mixture.
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