Just wondering how long I can go on a 2003 WR 450 Top End before a rebuild. 4 good seasons of racing in MD. Hare Scrambles mainly. not a lot of trail riding and a couple enduros. Checked valves in beginning of 2005 all ok. Still runs great, tons of compression, starts on first kick in most situations. Routinely change oil, oil filter and air filter. Run Golden Spectro 50/50 blend. Still on stock clutch. Any ideas???