Wayne.B wrote in
:

Did the old plugs look dirty or fouled
in any way?


What COLOR were the plugs? Proper color is a nice, DRY, light chocolate
brown if the engine is setup properly and none of the carb jets are
clogged.

The darker they get the richer, and more wasteful, it runs. If they are
wet, of course, it was the oil leaking by the worn-out rings, which usually
makes them black. In a 4-stroke engine they should never be wet.
Sometimes black also means the choke isn't opening or the carb float is
stuck or adjusted too deep.

If they are white or just off white, the jets are clogged with shellac and
the exhaust valve is slowly, but inevitably, eating itself from the
overtemperature exhaust. If it was so hot the plug was eaten away, well,
now is the time to tear off the carb and fix it, quick!

Never pull a spark plug that's been running over 20 hours without carefully
reading its condition and color. It's the finest "sensor" ever put in a
gas engine.

(Diesel folks, just ignore all this nonsense and enjoy the ride.)