hey i have been having trouble getting my bike to start. I havent ha it running since dec because i lost my key but when i found it i tried to start it and nothing. One of my friends started messing with the idle skrew to see if it would work and nothin. I have been moving the idle skrew back and forth and i dont get anything. It wants to fire but it will just fire two or three cylinders then shut off. What can i do? What would be the most possible cause?