Motorcycle Repair: What do I check next?, carborators, exhaust pipes

Question
My bike is starting up, but as far as I can tell only one cylinder is firing.  I have spark to all 4 plugs and I have checked the carborators and they seem to be clean.  Do you think it is electrical or something in the motor?  Only one of the four exhaust pipes coming out of the motor is hot the others do seem to have air flowing out it is just cold.

Answer
SInce you say you have 4 exhaust pipes I am going ot assumn you dont have a harley. I usually only answer questions on harleys, but I might be able to help.
remove a plug from each cylinder and turn the bike over while the plug is grounded. If you dont get a spark then you either have an ignition or coil problem.
Good luck and happy riding
Mike