Before I lay out the skinny on the WRs I want to disclaim my riding abilities. Over the years, I have owned the following bikes, 3 XR200Rs, XR250, XT650, XR400, KLX300, WR426 and now a WR450. I consider my self and advanced trail rider. I usually do one desert race and one enduro per year. I live in Emery County and ride the San Rafael Swell, Moab, 10 Mile and the Manti La Sal National Forest. Mods done to the 450. Grey wire, jetting at 48 PJ and 160 main. Fly bars, Scotts Tripple Clamp, Snorkel removed, left side panel cut to match right side. Stock exhaust. I done the same mods on my 426 except for jetting. WR426/WR450 STARTING: The electric start is nice, but it takes some getting used to. When kick starting the 450, give no throttle, but when using the electric start, the throttle needs to be slightly opened. The automatic compression is nice. Putting aside the automatic compression and electric start, the 426 starts as easy as the 450. POWER: The 450 is starved for air. The air intake does not do this bike any justice. The air box on the 426 was perfect. The 450 air intake on the top of the box is very limited. I removed the snorkel which took some effort and a dremile tool. I also cut away the ¼ inch lip that went around the air opening. I cut the left side panel where your hand goes to lift the bike. I have no idea why they did this, anyway, it does allow more air in and now the panel matches the right side panel. The battery is the reason for the small air intake. The battery takes up the room. Sure wish that I could have the entire top of the air box exposed. I drilled every possible hole that I could on top of the air box. As a last resort, I may need to put some holes in the side of my air box. Until this bike can get more air, an aftermarket exhaust will not have a substantial increase in power. The 450 seems to have a more friendly low end over the 426. Bottom line, the 450 is not any faster than my 426. SUSPENSION: The 426 and 450 are very similar. I could not tell much of a difference. GAS TANK AND SEAT COMBINATION: The 450 set up is very nice when compared to the 426. I had a YZ tank and seat combination on my WR and loved this set up. The stock 450 is very sleek and nice. I am disappointed with the smaller gas take. First chance, I am going to get a 3.1 gallon tank. WEIGHT: The 450 feels lighter and more agile over the 426. It is not a substantial difference, but it is noticeable. CROSSOVER PARTS 426 AFTER MARKET PARTS ON A 450: My skid plate bolted up to the frame better than it did on my 426. One problem. The drain hole was in the wrong place. I took my dremile tool and cut another opening. My 426 tripple clamp worked on the 450. My 426 YZ tank and YZ seat will not work. The 426 rear fender stock or YZ will not fit. Radiator shrouds will not fit. The front fenders will cross over. My front disk guard crossed over. My frame protectors worked with a minor modification to the left side. The 426 exhaust would not crossover. It could be done will some minor welding. OVERALL IMPRESSION: Was it worth the extra cost to by a 450? Not sure. My 426 was a fantastic bike. Jumping on the 450 and riding a 426, is like putting on a familiar pair of boots. I am glad I bought the 450 but the 426 is still in the race.