Quick discussion on healthy sparkplugs.

[MadMuz]

Whenever I have had trouble with spark plugs in the past, it has usually ended up being the nipple on the end being loose.... and if you tighten them up, usually they snap off

[Colinm-m22]

My Rotax was running rough and on investigation I found that my no 6 plug had a cracked electrode, but it looked perfect from the outside. http://www.youtube.com/watch?v=hnd7P7O_vEQNot saying its the only answer but it could help others.Regards,Colin