If your glow igniter is going dead then that could also be a problem. You must have a good glow starter to properly heat the plug. Mine has been used up to atleast twenty times in one day, and it still works a week later with no charge. You can get a good one for about twenty bucks at local hobby shops.
http://www3.towerhobbies.com/cgi-bin...?&I=LXJ800&P=0