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Good afternoon,

Cylinders 2,3 and 4 plugs are all light brown which is great. However, cylinder 1 is sooty. Engine runs great. Mags check fine.

Shouldnt #1st run the leanest. Being furthest from the carb?

 

7926_1_20200506_122200.jpg (You do not have access to download this file.)
7926_1_20200506_122323.jpg (You do not have access to download this file.)
  • Re: Spark plugs

    by » 6 months ago


    Oddly no. What you are looking at is not unusual, mine look much the same. I even called Rotec in Canada to ask about it and was told that it’s a characteristic of the carbureted 912.  Afraid I can’t say why though. Perhaps someone who knows can explain.


  • Re: Spark plugs

    by » 6 months ago


    Cylinder 1 sooty shows that some air is leaking from any joint , may be intake manifold o ring or nuts loose, or carburetor joints loose.

    Or spark plugs cable may be faults/worn that leak the current.

    Check it properly 👍.


  • Re: Spark plugs

    by » 6 months ago


    As long as I have known anything about spark plugs I have thought that a very light colored plug was running very lean (too much air) and a sooty spark plug was running very rich (too much fuel). Sooty could also mean the plug wasn't firing correctly. An air leak would cause a too lean condition. 

    Lately I've seen comments here saying an air leak causes sooty plugs. Have I been wrong all these years?

    Alan

     

     


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