is LD PLASTIC TUBING is WOODEN DOWEL 12 STAPLED TO DOWEL THREE PLACES Fig 8 62 Spark Plug Holding Tool 3 Using a 1 a spark plug socket remove the spark plugs NOTE To remove or loosen the center spark plugs it will be necessary to disconnect or remove carburetor throttle rod and use a universal drive on spark plug socket It may be desirable to use a special spark plug socket that is equipped with an internal O ring seal to grip the spark plug and avoid the possibility of dropping spark plugs into engine shroud assembly A tool may be fabricated as shown in Figure 8 62 to remove the spark plug after it has been loosened if a special spark plug socket is not available PORCELAIN INSULATOR INSULATOR CRACKS OFTEN OCCUR HERE SHELL i 035 PROPER GAP CENTER ELECTRODE FILE FLAT WHEN 1 SIDE ELECTRODE CADJUSTING GAP J BEND TO ADJUST GAP DO NOT BEND Fig 8 63 Spark Plug Detail Inspection Refer to Figure 8 63 Spark plug life is governed to a large extent by operating conditions and plug life varies accordingly To insure peak performance spark plugs should be checked cleaned and regapped every 5000 miles Worn and dirty plugs may give satisfactory operation at idling speed but under operating conditions they frequently fail Faulty plugs are evident in a number of ways such as wasting gas power loss loss of speed hard starting and general poor engine performance Spark plug failure in addition to normal wear may be due to dirty or leaded plugs excessive gap or broken insulator Dirty or leaded plugs may be evident by black carbon deposits or red brown yellow or blistered oxide deposits on the plugs The black deposits are usually the result of slow speed driving and short runs where sufficient engine operating temperature is seldom reached Worn pistons rings faulty ignition over rich carburetion and spark plugs which are too cold will also result in carbon deposits Red brown etc oxide deposits a consequence of the use of leaded fuel usually result in spark plug failure under severe operating conditions The oxides have no adverse effect on plug operation as long as they remain in a powdery state But under high speed or hard pull the powder oxide deposits melt and form a heavy glaze coating on the insulator which when hot acts as a good electrical conductor allowing current to follow the deposits and short out the plug Excessive gap wear on plugs of low mileage usually indicates the engine is operating at high speeds or loads that are consistently greater than normal or that a plug which is too hot is being used In addition electrode wear may be the result of plug overheating caused by combustion gases leaking past the threads and gasket due to insufficient compression of the spark plug gasket dirt under the gasket seat or the use of old gaskets Too lean carburetion will also result in excessive electrode wear Broken insulators are usually the result of improper installation or carelessness when regapping the plug Broken upper insulators usually result from a poor fitting wrench or an outside blow The cracked insulator may not make itself evident immediately but will as soon as oil or moisture penetrates the fracture The fracture is usually just below the crimped part of the shell and may not be visible Broken lower insulators usually result from carelessness when regapping and generally are visible In fairly rare instances this type of a break may result from the plug operating too hot such as encountered in sustained periods of high speed operation or under extremely heavy loads When regapping a spark plug to avoid lower insulator breakage always make the gap adjustment by bending the ground side electrode Never bend the center wire Spark plugs with broken insulators should always be replaced Cleaning and Regapping Clean the spark plugs thoroughly using an abrasive type cleaner All spark plugs must be of the same make and number or heat range AC46FF is standard equipment Use a round feeler gauge to adjust the spark plug gaps to 035 ng 8 64