What does it mean if the spark plug is dry and white?

Dry is good, but white is bad! It means that the engine is running lean, which will result in the engine running too hot and can cause serious engine damage (even seizure). Below is a guide to reading the spark plug color.

Black = Rich. The fuel/air mixture is too rich (too much fuel, not enough air).

Tan/Brown = Normal. The fuel/air mixture is correct.

White = Lean. The fuel/air mixture is too lean (too much air, not enough fuel).