Jake,

Black and dry, or black and gooey wet? If black and dry, it's too much fuel. If black and gooey wet, it's oil.

After you check all of your ignition system and adjust the valves, see if you still have the problem.

Then, if it's black and dry, check the carb function.

If it's black and gooey, you are getting oil in the combustion chambers, which does not belong there. If it is just valve seals, you could replace them without pulling the head. If it is the rings, then a proper repair would be rings or an engine rebuild.

However, if is it oil (black and gooey) and you don’t want to pull the engine apart, you could install non-fouling adapters into the spark plug holes, and install your plugs into the non-fouling adapters.

Non-fouling adapters used to sit on a display card behind the counter of every car parts store, but you don't see them much anymore. Ask at an auto parts store to see if they still have them. If they look at you like you are from another planet, fear not. You are just from a different time on this planet. I bet JC Whitney still has them if the auto parts stores do not.

When you look at the adapters, you will think it has to be a joke because they are so simple. Do not be fooled. I put them in a worn out Jeep and in a worn out Toyota years ago, and they are no joke. They work perfectly. They used to be about 49 cents each. Maybe today they could be up to $2.00 each.

I assume you are using the right plugs?

Charley