its a 2005 crf 450r. last time I rode it it was completely fine. it has a new top end on it with 55 hours. the exhaust valves were leaking when I last ride it.. didnt think it was a big deal. could this be a reason for a low compression? also, the bike doesnt want to start now, dont know if its the cold or what it is. what could be wrong? I sure hope it doesnt need another rebuild.... thanks.