Im thinking about selling my 07 450 and getting an 08 or 09 yz 450. Id like to avoid doing the top end/ four stroke rebuild. Ive been told they cost around 1500 to rebuild when they do need it. The bike runs great now. All Ive had to do so far for maintenance is replace the clutch, drive chain, sprockets, clean the oil and change/clean the filters and change many a tire. I bought the bike new in june 07, its been super dependable and fun. The bike has alot of hours. However its my first real dirt bike, Had an xr600 prior for about 6 mounths, so alot of the hours are begginer hours. Im thinking it better to sell than rebuild when it is finaly needed? Also, how much do you think an 07 that runs great is currently worth approximatley?