Plug gaps?

[CasiUSA]

What are the problems associated with plug gapping? i.e. what happens if I set it too wide or to narrow? is that terrible for the engine? and does it apply to water cooled motors as well?

[dgyver]

Too large or too small of a gap will not produce an effective spark to produce the best fuel combustion. So in turn you would have a lack of power, poor fuel economy, fouling plugs, & excess internal carbon build-up. I really does not matter what kind of motor it is. The results will be the same.

[Richard UK]

Wrong gap can also affect timing of the spark