Problem with 06 kawasaki kx250f?

[Brad]

So i bought an 06 kawasaki kx250f racing dirtbike when i bought the bike the previous owner was fixing something on the right side of the motor where the radiator tubes are there was a Y conector tubing piece missing but the bike still rode fine wihtout it i rode the bike for mabey 3 days and the third day i shut the bike off after a good ride everything was running fine the next morning i went to start the bike and it wouldnt start it sounded bogged down or something the next day i fixed the Y conector tubing piece and bought a new spark plug changed the oil but it still wont start what could be some possibilitys? thanks for any suggestions