Here are 4 possible causes for plug fouling:

     1) Weak ignition and/or retarded timing.

      - Check timing.
      - Check plug gap.
      - Check points for pitting (if badly pitted, the condenser must be replaced and the points smoothed or preferably replaced).

    If you remove the plug cap from the lead and rank the engine over, the spark should jump at least 8mm and be bright blue.

    2) Low compression.

    Due to leaking valves, badly worn bores or valves running without proper clearance.

      - Check compression.

    3) Too rich mixture.

      - Make sure the carb(s) are properly adjusted and clean.
      - Also check needle and seat for abnormal wear.
      - Plug(s) will be covered with soothy powder.

    4) Oil entering the combustion chamber in large volumes.

      - Should be noticeable through very high oil consumption.
      - Plug(s) will be wet and shiny with a pretty hard coat of brown/black deposit.


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