Membaca kondisi mesin melalui Spark plug (Busi)

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NGK Spark Plugs pamflet (1977)

The appearance 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 timing are properly adjusted.
This pamphlet is intended to assist you in correctly choosing your spark plugs and determining the performance condition of your engine.

Even plugs which present a good appearance such as those shown in Figures 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 the ignition system
  3. Oil pumping past worn piston rings and valve guides
  • The causes of sooty plugs like those shown in Figures 3, 4 and 5 are usually the result of :
  1. A plug with a too high heat rating is being used and the plug firing-end does not reach its self-cleaning temperature (above 400 ~ 450*C) due to light load conditions.
  2. Use of a too rich air-fuel mixture of richer than 8:1 ~ 10:1
  3. Trouble in the ignition system
  4. Improperly functioning cooling system resulting in excessive cooling
  • The firing-end burns illustrated in Figures 25, 26 and 27 may be a result of
  1. Too low heat rating, permitting the plug to exceed the highest limit for optimum operating temperature of over 850 ~ 1000*C due to excessively heavy load operations
  2. A too lean air fuel mixture
  3. Ignition timing too over advanced
  4. Abnormal combustion such as knocking
  5. Cooling system trouble, which causes engine overheating
  • Overheating conditions shown in Figures 28 and 29 are due to intense knocking and pre-ignition following situations identical to those in Figures 25, 26 and 27 where increased temperature of the spark plug firing-end results in melting of the electrode.

gambar 1 - Oil Fouled

gambar 2 - Oil Fouled

gambar 3 - Carbon Fouled

gambar 4 - Too Cold

gambar 5 - Too Cold

gambar 6 - Cold or Rich But OK

gambar 7 - Cold or Rich But OK

gambar 8 - Cold or Rich But OK

gambar 9 - Good

gambar 10 - Good

gambar 11 - Good

gambar 12 - Good

gambar 13 - Real Good

gambar 14 - Best

gambar 15 - Best

gambar 16 - Best

gambar 17 - Best

gambar 18 - Good

gambar 19 - Good

gambar 20 - Good

gambar 21 - Kinda Hot But OK

gambar 22 - Hot or Lean But OK (?)

gambar 23 - Hot or Lean But OK (?)

gambar 24 - Hot or Lean But OK (?)

gambar 25 - Too Hot or Lean Pre-Ignition Range

gambar 26 - Too Hot or Lean Pre-Ignition Range

gambar 27 - Too Hot or Lean Pre-Ignition Range

gambar 28 - Too Hot or Lean Pre-Ignition Range

gambar 29 - Too Hot or Lean Pre-Ignition Range

gambar 30 - original scan of the text

-- end --

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