Top-of-the-line motocross bikes get pretty significant improvements each year, and every few years they undergo a total redo. Honda's first CRF450 was introduced in 2002 to stellar reviews and many "bike of the year" awards, solidifying the validity of the 450cc four-stroke motocross market. It received small upgrades in 2003 and '04 until an all-new frame was introduced in '05. Two years again passed before upgrades to motor and suspension take us to the 2008 CRF450R.Our typical testing involves riding each new year's model with the one we've had from the previous year to help identify the changes. It's often easy to feel how much better the new bike is; other times the changes may take a bit of getting used to. Sometimes the heavily used state of a previous year's test bike makes the new bike feel just that-new and better. For this science experiment of tests we recruited a 2002 and a 2005 CRF450R. Both were largely stock, except for some minor suspension revalving. We had Honda freshen them with new air filters, chains and sprockets. The valves were checked (all were in spec), and new plastic replaced the worn original stuff. We changed the oil and fitted Dunlop 745s to all three bikes.The first step of the test was conducted in front of the radar gun to see if there were any changes in the bikes' speed. It showed the differences were minimal and, surprisingly, both of the older bikes had game on the starting line. When we rode the bikes wide-open like a start, there wasn't any notable difference in the way they pulled. But in the roll-on of third gear, where the throttle position varies, the newer the bike, the quicker it felt like it started to pull, but the radar gun largely called it a tie. Honestly, that 2005 isn't looking so bad to the gun.When we hopped on these bikes and took to the track, the variations really began to show. The first trait that stands out is a combination of weight feel and agility in handling. The '02 feels the heaviest, mostly through the handlebar and whenever you throw the bike from side-to-side. The bike feels longer in a good way and more stable. It also feels a lot more planted and not as loose on the ground. You notice the wider width in the frame rails between your legs in addition to the seat having a little more padding which you sink into more in the turns. The '08, on the other hand, is easily the lightest-feeling. It takes a lot less effort to turn the bar, even with the steering stabilizer set at or near the stiffest setting. The bike doesn't feel as planted or as stable, but it isn't lacking in traction nor does it do anything we'd call unstable. If you go from the '02 to the '08, it definitely takes some getting used to. And the more experienced or higher level the rider was, the more he appreciated what the '08 was doing. As expected, the '05 sat in the middle, a hair closer to the newer bike than the older edition. It felt almost as light when flicking side-to-side but had a slightly more weighty feeling in the handlebar. The motor was sitting between the other two, almost exactly like a bridge.Next we noticed the suspension. For sure, the newer the bike was, the faster the suspension movement felt. This is in a time when the current Hondas are getting beat up for a harsh-feeling front end, yet the '08 was the most supple of the three. Sure, we felt a little feedback through the bar on the newest bike, but you get as much of this, if not more, on the older bikes; it's just a little different. The '02 has a much more "dead" feeling in the suspension, not really springy or active. It absorbs the bumps fairly well, handles the jumps and lets the bike track pretty decently. But the best way to describe the improvements is the speed at which the suspension reacts to whatever the track throws at it. The '02 isn't giving you a quick response (measured in milliseconds, not scientifically, but through feel) on every bump. Through the stiffer frame and with help from compliance in the tires, the bike is doing what it should, but CRFs have definitely gotten better in the last six years. The '05 is a leap in the right direction as the frame got a little more flex built in, and that takes some of the bump feel out of the ride. Then you step up to the '08, and it's a lot better on both ends of the spectrum. It takes the ripples out of the ground more naturally than the others, especially through the rear shock, plus it resists bottoming more. It takes the jolt out of the really hard hits. Yes, the '05 again sits right in the middle here, and since the chassis and suspension components are very similar between it and the '08, the '05 can certainly be modified to work at a very high level.