Below are taken from dansmc.com regarding different colors of sparkplug to determine if you have too lean or too rich air fuel mixture
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The apperance of the firing-end of a spark plug graphically reflects the condition of an engine.
the suitability of the spark plug heat rating and whether or not the carburetor and ignition time are properly adjusted.
This pamphlet is intenede to assist you in correctly choosing your spark plugs and determining the performance condition of your engine.
*Even plugs which present good appearance such as those shown in picture 6-24 can quite often be covered with a lead deposit which causes misfiring.
*Wet plug firing ends such as shown in figures 1-2 are normally attributed to one of the following causes:
1. Excessive choking
2. Trouble within ignition system
3. Oil pumping past worn piston rings and valve guides.
*The causes of sooty plugs like those shown in figure 3,4,5 are usually result of:
1. A spark plug with a too high heat rating is being used and plug firing does not reach its self cleaning temperature (above 400-450 degrees celcius) due to light load conditions.
2. Use of too rich Air Fuel mixture of richer than 8.1-10.1
3. Trouble in the ignition system
4. Improperly functioning cooling system result in excessive cooling.
*THe firing end burns illustrated in figures 25,26,27 may be a result of:
1. Too low heat rating permitting the spark plug to exceed the highest limit for optimum operating temperature of over 850-1000 degrees celcius due to excessively heavy load operations.
2. A too Lean Air Fuel mixture
3. IGiniting timing too over advanced
4. abnormal combustion such as knocking
5. Cooling system trouble which causes engine overheating.
* overheating condidtions shown in figures 28 and 29 are due to instense knocking and pre-ignition following situations identical to those in figures 25,26,27 where increased in temperature of the spark plug firing end results in melting of the electrode.
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The apperance of the firing-end of a spark plug graphically reflects the condition of an engine.
the suitability of the spark plug heat rating and whether or not the carburetor and ignition time are properly adjusted.
This pamphlet is intenede to assist you in correctly choosing your spark plugs and determining the performance condition of your engine.
*Even plugs which present good appearance such as those shown in picture 6-24 can quite often be covered with a lead deposit which causes misfiring.
*Wet plug firing ends such as shown in figures 1-2 are normally attributed to one of the following causes:
1. Excessive choking
2. Trouble within ignition system
3. Oil pumping past worn piston rings and valve guides.
*The causes of sooty plugs like those shown in figure 3,4,5 are usually result of:
1. A spark plug with a too high heat rating is being used and plug firing does not reach its self cleaning temperature (above 400-450 degrees celcius) due to light load conditions.
2. Use of too rich Air Fuel mixture of richer than 8.1-10.1
3. Trouble in the ignition system
4. Improperly functioning cooling system result in excessive cooling.
*THe firing end burns illustrated in figures 25,26,27 may be a result of:
1. Too low heat rating permitting the spark plug to exceed the highest limit for optimum operating temperature of over 850-1000 degrees celcius due to excessively heavy load operations.
2. A too Lean Air Fuel mixture
3. IGiniting timing too over advanced
4. abnormal combustion such as knocking
5. Cooling system trouble which causes engine overheating.
* overheating condidtions shown in figures 28 and 29 are due to instense knocking and pre-ignition following situations identical to those in figures 25,26,27 where increased in temperature of the spark plug firing end results in melting of the electrode.
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