Yesterday was the day that every magazine editor was impatiently waiting for - the arrival of the 2008 Suzuki RM-Z450. To say that Suzuki’s flagship motocross bike is all new for 2008 would be a severe understatement. There are very few parts that the 2007 and ‘08 model share, such as the air filter and oil filter. Beyond that, the fuel-injected RM-Z450 was built from the ground up.
The MXA wrecking crew met with Suzuki personnel at Perris Raceway in southern California to sling a leg over the new RM-Z450. At first glance, we immediately noticed the “Fuel-injected” sticker on the side panel. Unless you’ve been studying glacial shifts in the ice caps down at the South Pole for the past year or so, you’ll know that Suzuki has been trying to zero in on developing a fuel-injected motocross bike. Alas, the time has finally come.
Also noticeable were the 5mm wider footpegs, which have been designed to ward off mud from caking up. The two-tone molded plastic radiator shrouds (sans rivets) were a nice touch, as was the gold chain (o-ring) and axle blocks. The 450 also comes with Bridgestone’s new M403/404 combo, and the rear tire is a 110 (120 last year).
Now it’s down to the nitty gritty. The RM-Z450 has a five-speed transmission (and not just a four speed with a top gear added on for desert riding). It should go without saying that the gear ratios are different from the 2007 RM-Z. Gearing is 13/50. Suzuki also increased the flywheel inertia, changed the intake port and intake cams (port angle changed from 10 to 25 degrees, cam timing changed, and optimized the port shape). The exhaust port and exhaust cams were modified, and the 450 has a semi-dry sump design. Also, the intake port is longer and straighter than the ‘07 design (this has been changed to work better with the fuel injection, which is said to deliver smooth, quick response).
Which leads us to fuel injection. While the fuel pump is housed inside the 1.6-gallon aluminum gas tank (to make the pipe routing simpler), the Keihin-made throttle body has a 12-hole fuel injector sensor. Also on the throttle body is a progressive link, which was designed to create a more gradual throttle opening at low throttle (to increase engine controllability). Also on the throttle body is a choke switch for cold weather. The choke switch can also be turned to either raise or lower the idle. As for changing the electronic fuel injection, expect a bevy of companies to come out with technology that makes it possible (apparently Yoshimura almost has something ready for the market, called the MX Tuner). To get the complete scoop on Suzuki’s fuel injection system, be sure to check out the March 2008 issue, which will be on newsstands soon.
Is the 2008 RM-Z450 the bike to beat? Will every other manufacturer have to drop their carburetor and step up to the plate now that Suzuki has successfully incorporated fuel injection into a motocross bike? We hate to have to do this to you, but read the upcoming issue of MXA to find out.
Suzuki Motorcycle tests