[AT] Spark Plug Fouling Ferguson TO20

[Szakaluk]

Request advice or suggestions on what I can do to reduce fouling on #4 spark plug on my 1951 Ferguson TO-20, here or to me direct.
I've had it since 1990, only use it 8 or 10 hours a year.  Field mowing, snow removal, wood splitting (auger).
Using 10W30 oil, Champion D21 plugs, which I understand is a hot plug for this application.
At first, I could go twenty or 25 hours between plug fouling/cleaning.  Only #4 is a problem, others are fine. Using very little oil.

Now I need to clean #4 every six or seven hours.
Appreciate your suggestions on how I can reduce this issue.  I know someday the engine should be worked on, but with this limited annual use I can't justify tearing it down.
Heavier oil?Different plugs?  If so, on all cylinders, or just #4?Oil additives?Other thoughts?
Thanks in advance
Steve Zakalukszakaluk at aol.comFalcon, CO
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