My son turned pro in November. He has been racing YZ250F's ever since he moved up to big bikes. Yes he races a 250F in the 450F class. We are looking at getting him a 450F after the first of the year. We are leaning towards the RMZ 450 because I can get them 08/09's (brand new) for around $5000.00 but I did some research and the engine parts are rediculous compared to the Yamaha's. I just want some input from those of you that own 08 or 09 YZ450F's. Any issues? I usually do a top end on the 250F's every 40 hrs along with the timing chain. Do you guys do them any less than that or does that sound about right for a 450F as well? Any other opinions on the bikes would be appreciated too.