Small Engines (Lawn Mowers, etc.): spark plug, air fuel ratio, air fuel mixture

Question
Hello Eric,

I have a homemade woodsplitter. It has an old (1972) briggs
engine. I had trouble starting it. I took out the plug and
it had carbon deposits on it. I had not done anything to it
except add oil. Could this be caused from too much oil,
or is this more of an air/fuel mixture or the carb?
It is a 4 stroke engine.

thanks
tim

Answer
If the carbon was dark black and sort of moist looking that is oil.  If it black and dry looking then the carb air/fuel ratio is too rich.

Have you ever replaced the point, cleaned the combustion chamber/head, or checked and cleaned the valves?

Eric