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TransWorld Motocross Gets You Up Close and Personal with the 2006s

Each year, fans at the opening round of the All Japan National MX Championship Series are treated to something that no Americans have enjoyed on a regular basis for 19 years now. Though we’ve had the pleasure of checking out works four-strokes from Honda and Yamaha thanks to the one-time exemption rule, works bikes have effectively become a thing of the past since the AMA adopted the production rule for motocross racing in 1986. In Japan, however, no such rule exists, and as a result, the Land of the Rising Sun is the best place to check out a prototype or radically exotic bike in action. TransWorld Motocross attended this year’s season kickoff at Meihan Sportsland in the Nara Prefecture, just outside of Osaka, Japan, and here’s what we saw…


We were surprised to find production-based bikes in the Honda pits, especially since the Red Riders have been known to campaign some of the most radical bikes in the past, including an automatic transmission-equipped CR250R back in the day. The usual assortment of special parts adorned the CRF450Rs campaigned by team riders Kazumasa Masuda and Kenjiro Tsuji, but it was the CRF250R of Yoshihide Fukudome that was the most interesting. Equipped with two mufflers, the single exhaust header splits into two mid-pipes behind the shock, but in front of the airbox mud flap. With a strict 98db competition sound limit in Japan, most of the teams opt to run OEM exhausts. The reason for the twin-muffler design? Rumors of an even lower 96db sound limit in the MFJ’s near future have Honda engineers planning ahead. Though the system on Fukudome’s bike measures 98db, Honda staff on hand told us that the dual muffler setup provides better power than a quiet single pipe ever could. Fukudome, meanwhile, claimed that the system offered a better feel on the track, giving the bike a more balanced feel, especially in the whoops. Though it is doubtful that we’ll see an exhaust system of this sort in production in 2006, don’t be surprised if such setups are the future of our sport. Less noise is a good thing.


A works version of the RM-Z450 was campaigned throughout last year’s Japanese series, and the bike that factory rider Takase Tanaka is campaigning this season is production based, albeit with some preproduction ’06 goodies. In its sophomore year, expect the big Suzuki thumper to appear largely the same, but boast some frame and chassis changes that will help it handle even better. The frame welds behind the steering stem of Tanaka’s bike were different than those of a production ’05 bike, and reports have the new construction targeted at yielding more torsional flex to improve cornering even further. We also spotted radically different head stay motor mounts on the number two machine, which are likely designed to compliment the more forgiving chassis design. Works Showa suspension graces both ends of the factory Suzuki, with massive 51mm tubes doing the duty up front. Suzuki was one of the few teams to utilize an aftermarket exhaust on their race bikes. The Yoshimura systems found on the team machines featured much larger end caps than those found on production Yosh pipes, obviously to help keep the sound down to legal limits.


The KX250F and KX450F works bikes both feature aluminum chassis that bear an undeniable resemblance to those found on the production ’05 Hondas. While the powerplant inside the KX250F chassis looked to be the same base model as those found in the current 250F, the motor in the KX450F was-obviously-all new. The powerplant is 449cc and features a double-overhead cam design and four valves. From the rear, the bike seemed to be a tad bit wider than the red and yellow competition, though without sitting on it, one could not be sure. We were surprised to see works Showa suspension on the KX250F, as all production Kawasaki motocrossers come equipped with Kayaba componentry.. In Meihan, Tetsuya Mizoguchi looked very impressive on the KX250F, finishing second in the first moto after an inspired come-from-behind ride, while Tomonori Nakamura piloted the KX450F to fourth in the 250cc division. While the 2006 Suzuki RM-Z250 will enjoy the same new chassis design as the KX250F thanks to the Suzuki/Kawasaki strategic alliance, the KX450F is and will be a Kawasaki-only product.


As ridiculous as it sounds, Yamaha management kept the aluminum-framed YZ250F and YZ450F hidden inside a clear plastic tent in the pits in order to keep photographers from getting close to it. You can’t take a tent with you to the starting line, however, and we were able to get a good look at the new aluminum chassis that grace both machines. Like the aluminum-framed two-strokes in the Yamaha line, the YZFs both maintain traditional frame design, rather than opting for the semi-double cradle design of the Honda, Suzuki and Kawasaki. Painted blue to look like a production steel frame, the new chassis did not feature the radical cut-out waffle pattern near the swingarm pivot that the production two-stroke frames have. A full-coverage radiator shroud replaces the old exposed fuel-tank design, and both of the thumpers looked sleek and thin. Tadashi Kagimura gave the YZ250F works bike a successful debut at Meihan, winning the second moto and placing second overall on the exciting new machine. Shinobu Idehara, meanwhile, was not as successful aboard the YZ450F, as he never matched the pace of the front-runners and was credited with 12th overall.