I just bought an 02 CRF and went with this bike because you can still Calif green sticker the 02's and ride them off road, the 03's and 04's are Calif red sticker bikes which means they are illegal to ride on public land (sucks). I have read everything about the CRF450 I could get my hands on and as far as I know the differences between the 02 and 03 are as follows. The 03 went with a different linkage which pushed up the a$$ end which made the forks steeper and improved turning, they also changed the subframe to keep the 02 seat height. The cam, ignition, muffler, and carb received mods to increase bottom end and throttle response. The forks are 10mm longer and have a little more travel. The 02 airbox leaked and this was fixed for 03, it also flows a little better and has a larger element. The shifter is different (longer I believe) and the bars are slightly further forward and the seat slightly taller to open up the cockpit a little. All in all there were no huge wholesale changes and modified 02's are still very competitive even against 04's. HTH