The 2008 RM-Z450 proudly stood in the corner of a community center conference room. From a few yards in front of it, as Suzuki's press representatives, Japanese engineers and PR gurus encircled me with greetings and salutations, I could almost hear it apologize.
I think the big yellow guy was truly regretful for being late to the 450 game. To make up for it, his friends in attendance really talked him up. They spoke of the revolutionary technology involved in his fuel-injection system. They raved about a redesigned frame, chassis and suspension. And they mentioned, not briefly, about a list of engine and transmission upgrades that would make even a non-fuel-injected model proud.
Quickly we learned that the 2008 RM-Z was more than a throttle body. But we hear a lot of things from a lot of people about a lot of bikes. We know the best way to tell you about the RM-Z is to take it out on the track. And that's where we've been.
The 2008 RM-Z450 is a great motocross weapon. The fuel-injection system works flawlessly in delivering a smooth progression of power from the historically manageable engine. The overall power output won't knock the socks off some of the more aggressive bikes in the class but its usability is out of sight. The EFI system is so efficient and seamless in its performance that you can slam the throttle open at any time and the motor instantly responds. It's actually a lot of fun to just rev the beans out of the bike in hopes of a negative reaction. But it won't flutter, sputter or stall. It just barks, immediately, no matter what.
The bark-to-bite ratio is right on for most riders, too. With the RM-Z, the bite is strong. Traction-inducing power is encouraged by a rising-rate linkage in the throttle body that opens the valve slowly at first then more rapidly as you get closer to wide open. The grip is enhanced further by a torquey low to midrange (thanks to slightly higher compression and a reworked cylinder head). Thankfully, a nicely spaced five-speed tranny replaces the track-only four-speed of the big RM-Z's past. Now this bike has some legs to go with its power.
The overall power delivery isn't unlike a lot of factory-level race bikes we've encountered in the past year, including Ricky Carmichael's. Top teams and the fastest riders in the world understand that peak horsepower numbers are only as important as efficient delivery. Power needs to build fluidly or else traction will suffer. The RM-Z seems to take that direction from the crack of the throttle on up and backs it up with a decent helping of power on call at any time. It can also be as aggressive as you want based on how you turn the throttle, and you can be crazy with it without any "jetting" consequence. The bike revs quicker than most of our testers prefer in the upper-mid and then it lets loose up top in a flurry. It's not uncontrollable, just quick getting through at the top. The easy solution here is to shift quickly and use the clutch. By starting your straightaway a gear high-to keep the power in the meat-you'll be happier than revving out too soon. Also, you need not worry about bogging or hesitation out of the corners when a gear high, for sure. The EFI makes lugging worry-free.
By far, the most impressive aspect of the fuel-injected motor is the instantaneous throttle response and traction-hungry delivery. From the deep ruts of Perris Raceway the day of the intro to the tighter confines of the harder-packed Piru Raceway, the RM-Z was nothing short of amazing in the traction department. While they're not a true component of the EFI system, the heavier flywheel mass (required to charge the system) and more flexy chassis are undoubtedly aiding the buttery flow of juice to the rear tire.