Just wanted to post this cause it feels good when you make the right choice.. I bought my '04 yz450f in November 2003. I have changed the oil and cleaned the air filter semi regularly. I have also beat the piss out of this bike and me being 6'5" 250lbs, it might be a little tougher on the bike than the average rider. I have raced the bike, bounced off the rev limiter and let the bike bounce on several occaisions from missed jump attempts. I just took the bike in for a service and first valve check and..... perfect! in factory specs, and no adjustments needed. I watch friends riding or not riding(cause they are in the shop getting a 10-hour valve adjust or replacement) other bikes and I'm glad I made the right choice- the guys at Yamaha are to be commended for an excellent product, and if you chose a Yamaha congrats on a good purchase! P.S. my next bike will probably be an Aprilia RXV 450 because it looks like a bad ass bike, AND I don't need another Yamaha cause this one still works great.