ok so im selling my 01 rm125 and upgradeing to a four stroke. I do just as much trail riding as i do track. Would i be better off with a 1999 yz400f for 1100 bucks or should i wait till spring and get a 06 or newer 250f for around 2000-2500? Are there any particular problems with the yz400 i should watch out for? Also how do they compare to 450s? What are the main differences between the 400 and the 426? any information is greatly appreciated.