The huge changes to Yamaha's '05 YZs might lead you to believe the motocross effort soaked up all the R&D;, but it looks like there was plenty left for the off-road bikes as well. Yamaha's newly released WRs feature a slew of changes, both major and minor, aimed at creating lighter, more agile and more user-friendly machines. We got our grubby paws on the newly released WR 250 and 450 at California's Hungry Valley and immediately headed out for some bushwhacking.The biggest changes Yamaha emphasized were a lowered center of gravity and lowered seat height for both the 250 and 450. WRs have a history of being tall and top-heavy, but the '05s are a marked improvementit looks like the chronic problem has been solved. The WRs now carry their (lighter) weight much lower. Yamaha raised the steering head tube, but the fork is the same length, so the engine and more importantly the crankshaft are carried lower. Plus the shock is 3mm shorter, which balances out the bike and makes it lower overall compared to 2004. Overall, the seat height was decreased by 10mm on the 250, and 20mm on the 450. YZ shrouds and radiators complete the package by slimming down both bikes. Both models were much more willing to change directions in tight conditions. It was much easier to get leaned over in corners and maneuver through thick, tight brush.We didn't actually test the bikes in showroom stock condition. We replaced the WR throttle stopsthat limit the throttle opening to about halfwaywith YZ units that allow full throttle travel. We also removed the new-for-2005 tiny end baffle and unplugged the grey wire under the tank, since that was the way we rode our 2004 bikes, and it was the most equal comparison. The WR250F received an increase in power while the focus on the 450 was to refine its big power for easier roll-on. The 250 has more bark and decent bottom-end grunt, but best showcases its new power on the top endit screams. The 450's bark was partially calmed by reducing the compression ratio. It still has big power, but now comes in a more manageable package. The lower center of gravity coupled with the smoother low-to-mid delivery made huge improvements in the 450s agility.The WRs received new 48mm forks, although not the same KYB fork as the other '05 blue bikes. The beefy new front suspension is much more rigid than the plush feel of the '04s. With the stock settings, the front end was too stiffpushing in sand washes and dancing around on rocks or bumpy hard-pack. We softened up the compression between two and six clicks depending on the size and speed of the rider. We also went out two clicks on the fork rebound. The action of the fork and the steering precision of the bike is very closely tied to the sag. You'll want to be careful to set it between 100 and 105 millimeters. The shock soaked up chop fairly well, and pounded through whoops better than ever.Yamaha also addressed EPA an CARB regulations in their re-design. The new USFS-approved aluminum exhaust with spark arrestor is Federal noise level legal at 82dba. With the baffle out, it still registers under 96dba, meeting California regulations. The 450's newly designed air induction system also makes it green-sticker ready (a much-welcomed change for Californians tired of being shut down the instant rangers catch a glimpse of blue plastic). Expect the 250 to be green sticker-able in '06.Look for the full test on both Yamaha WR's in the February issue of Dirt Rider Magazine.