i went out riding the other day a noticed that i had a hard time starting my bike. i figured that it was just cold or something. i finally got it started and rode really hard doing my drills, (starts and turnes). progressivly thoughtout my riding session the bike got harder and harder to start. while it was started i really didnt notice anything wrong. now the dam thing wont start at all. is it my valves? if so how can i illiminate this problem and prevent it from happening again? CRF 250R (2006) ALL STOCK.