2 days ago bike started up and ran great. Today I took the gas tank off to change the air filter and put the tank back on. Tried to start it and it just cranked over and over would not start. Take the tank back off and the air box to see if I knocked anywires lose or anything. All the connections seem fine, so I pulled a plug out and check for spark. Not getting any spark to all 4. Anyone know what the problem could be? Any help will be appreciated. Thanks