In motocross, confidence is everything. So instead of a risky full redesign, Suzuki chose to hone its trusty RM-Z450
motocrosser ($8749). Since it debuted eight years ago, the fuel-injected RM-Z has received a steady stream of updates in an effort to extract the most performance from its battle-tested platform. For 2015 the RM-Z450 gets a new frame and works-style Triple Air Chamber (TAC) fork (see sidebar) from Showa.
Even though its fuel-injected, getting the yellow bike’s water-cooled Single fired to life hasn’t been the easiest, requiring a deliberate and well-timed kick to get it lit on the first try. So engineers went back to the drafting board in Japan to improve the starting procedure. An inch-longer kickstarter lever was fitted and matched to revised gears, exhaust camshaft and decompression mechanism. This enabled the deletion of the manual and thumb actuated hot-start lever.
“The ’14 model was a bit hard to start,” remembers MotoUSA RM-Z test rider, and three-time X-Games gold medalist, Vicki Golden. “The ’15 model, I’ve watched people start it with their hand which is pretty insane for a 450.”
) Not only is the kickstarter more than an inch longer, some of the engine’s internals have been re-worked to make it easier to start, hot or cold. (Center
) The SFF-AIR front suspension separates air spring duties (right leg) with an inner, outer air chamber (pictured), and balance chamber. A conventional damping cartridge inside the left leg. (Bottom
) Look carefully and you’ll see that the frame’s downtubes have less material for added chassis flex.
The RM-Z still offers the ability to tune the engine’s powerband with simple and easy-to-use plastic couplers. In the standard setting throttle response is precise, doling out a thick and immediate spread of power at all revs. While Vicki prefers the standard setting, if seeking extra engine ‘oomph in loamy terrain or deep sand choose the ‘white’ coupler, or vice-versa, for more mild response on hard-pack terrain install the ‘grey’ coupler.
“I did notice that the bike was quieter,” says Vicki. “The bike sounded quieter [so] you’d think it would be slower, but it was actually fine power-wise. It felt all the same as last year’s bike.”
Vicki did file one complaint though, saying that she’d go larger on the rear sprocket if it was her bike. However the rest of the powertrain, including the five-speed gearbox and cable-triggered clutch, all performed as advertised. We were especially keen on the transmission’s secure engagement between cogs, which helps eliminate mis-shifts. As Golden mentions, the muffler was re-worked in order to make it quieter for riding in noise-sensitive areas.
Any racer will tell you that a good start is one of the keys to winning a race. Accordingly, Suzuki has fitted its newly developed electronic Holeshot Assist Control. The rider can choose between one of two modes (as well as ‘off’) via a small clear button next to the engine kill switch: ‘A’ mode (slowly flashing indicator light) is designed for use on slippery surfaces and/or concrete starts. It retards engine timing for 1.2 seconds after launching or until the motorcycle is shifted into third gear, whatever happens first. ‘B’ mode (indicator light rapidly blinking) is for more explosive power on high grip terrain. It returns to standard ignition timing 4.5 seconds after launching or upon shifting into fourth gear.
“B-mode here was almost too aggressive,” thinks the Moto X gold medalist. “With a holeshot device though that thing would be a game changer. It would be hard to say if I would use it. X-Games normally is more slippery. But it would be a good feature to have—to be able to try both and see which one would work better. Either mode would be better than not having it.”
While we like the RM-Z’s motor package, the evolution of its chassis is what really
RM-Z450 Suspension Settings
Inner Chamber: 175 psi
Outer Chamber: 0 psi
Balance Chamber: 175 psi
Compression: 8 (Turns out)
Low-Speed Compression: 12
High-Speed Compression: 2
stands out. Where the ’13 and ’14 had a rigid feel with a single-sided coil spring fork that was tricky to set-up, Suzuki’s latest chassis is far more compliant. To do this, the frame down tubes (cradle area just forward of the engine) have less material (Suzuki claims a 4% weight reduction) and the inner ribbing on each spar (area behind engine where the swingarm links) were modified for more flex. New rear axle blocks offer another slight rigidity tweak. Complementing this is an all-new air fork from Showa that is virtually identical in design to the works kit used on the Yoshimura and RCH racebikes (aside from ultra-slippery coatings and oil).
Perhaps the greatest attribute of the ’15 RM-Z is the added confidence it gives its rider as three-time X-Games gold medalist, Vicki Golden demonstrates.(Center)
With the release of the Single Function Fork Triple Air Chamber (SFF-TAC), Shows joins its arch rival Kayaba in the air suspension game. But contrary KYB’s single chamber set-up, the Showa unit incorporates a triple air cavity design. (Right)
The Suzuki’s engine blends the best of both worlds: Not only is it smooth and tractable, it’s got plenty of snap throughout the rev range.
“I’m more of a rider that prefers a plusher set-up,” says the 150-pound Golden, who represents the lighter side of rider spectrum on a 450. “This bike is night and day different compared to the ’14 model. The ’14 model was on the rigid side. With their new frame and the suspension—the whole set-up is just so much better. The bike is stupid good at cornering. I feel like you could probably ghost ride that thing into a rut and you’d be fine. It corners on its own.”
“It’s so much better than the single-sided [coil spring] forks,” she adds. “It just works way better and makes the bike corner a whole lot better. Even the smaller bumps—it felt like you couldn’t even feel the bumps that were there. The bigger bumps were a little bit more rigid on initial impact but once you got past the rest of the stroke it was a lot better.”
) Although it only lost two pounds on the scales, with the addition of the SFF-AIR front suspension and updated frame, the RM-Z450 feels lighter and more nimble than before. (Center
) Even though it doesn’t offer the same level of control adjustment we appreciate the RM-Z’s purposeful and well throughout ergonomics. (Bottom
) Greater adjustability and almost infinite fine tuning are benefits of Showa’s TAC fork. However it could also be easier to get ‘lost’ in set-up.
The RM-Z’s extreme agility has always come with a price: stability. However our lady tester claims the chassis enhancements have also improved overall stability: “I noticed last year’s model was a little bit scary in the high-speed stuff. But this year’s model, high-speed, low-speed, tight, technical, it all works so much better.”
Although it lacks a degree of handlebar and footpeg adjustability as offered on other brands, it never bothered us. And aside from selecting a different bar bend we’re happy with the yellow bike’s cockpit as it’s an effective platform to work from.
Braking power from the wave-style disc brakes is adequate, but a little extra feel and friction force could is an area where Suzuki could stand to make some improvements. Although they are getting a little dated, we still love the versatile and surefooted grip from Bridgestone’s trusty M403
/M404 intermediate terrain tire
From the outside it may appear the same, but make no mistake: Suzuki’s latest iteration of the RM-Z450 is a considerably improved track weapon. Though it cut just two pounds from the previous model (247-pound claimed curb weight) with the chassis’ improved rigidity and the front suspension’s enhanced action, the yellow bike is more cat-like, allowing the rider to put in fast laps with greater confidence.
- Wide and very precise range of fork adjustment
- Incredible handling
- Smooth, highly useable powerband
- Purchase price doesn’t include fork air pump
- TAC fork can require more set-up time
- Brakes could offer improved feel and power
2015 Suzuki RM-Z450 First Ride