Yamaha F250 LF250 Owner's Manual

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Contents

Maintenance51EMU30770Cleaning and adjusting spark plugWARNINGEWM00560When removing or installing a spark plug,be careful not to damage the insulator. Adamaged insulator could allow externalsparks, which could lead to explosion orfire.CAUTION:ECM01510 Do not use any tools to remove or installthe spark plug cap, otherwise the igni-tion coil coupler may get damaged. Thespark plug cap may be difficult to re-move because the rubber seal on theend of the cap fits tightly. To remove thespark plug cap, simply twist it back andforth while pulling it out; to install it,twist it back and forth while pushing itin. Be sure to use the specified spark plug,otherwise the engine may not operateproperly.The spark plug is an important engine compo-nent and is easy to inspect. The condition ofthe spark plug can indicate something aboutthe condition of the engine. For example, if thecenter electrode porcelain is very white, thiscould indicate an intake air leak or carburetionproblem in that cylinder. Do not attempt to di-agnose any problems yourself. Instead, takethe outboard motor to a Yamaha dealer. Youshould periodically remove and inspect thespark plug because heat and deposits willcause the spark plug to slowly break downand erode.1. Remove the bolts that are securing theignition coil cover, and then remove thecover.2. Remove the bolts that are securing thespark plug cap, and then remove the cap.3. Remove the spark plug. If electrode ero-sion becomes excessive, or if carbon andother deposits are excessive, you shouldreplace the spark plug with another of thecorrect type.4. Before fitting the spark plug, measure theelectrode gap with a wire thicknessgauge; adjust the gap to specification ifnecessary.Standard spark plug:LFR6A-11