have you done a compression test or checked the valve clearances?is it fuel injected?i would suggest taking the air filter cover off and getting a water atomiser and spraying a mist of petrol in the non running carb(intake side) and see if it chirps up for a second if it does then its the carb or fule injection system ,have you rested the plug onto the head or rocker cover while its still in the ht cap to see if it has a spark on that cylinder?
adam bike doctor
December 2009