Suzuki has let the cat out of the bag on its 2015 Suzuki RM-Z and RM motocross machines, with its flagship RM-Z450 receiving substantial changes while the RM-Z250 and RM85 (two-stroke) are basically unchanged except graphics.

RM-Z450
The RM-Z450 may not have a lot of improvements, but the two that Suzuki did incorporate are big ones, aimed at sharpening its on-track performance. For starters, Suzuki has added what it calls Suzuki Holeshot Assist Control technology—launch control, in layman’s terms—a system with similar intent to the one Kawasaki introduced on its KX450F two years ago. The Suzuki Holeshot Assist Control features two modes that alter ignition timing to tailor the power to the rider’s needs. In A Mode, the RM-Z retards the ignition to offer less wheel slip in hard-packed or slippery conditions. B Mode offers more aggressive mapping for when starting gate conditions are conducive to more traction. In either mode, Suzuki Holeshot Assist Control is programmed with specific commands that return ignition timing to normal operation and let riders power into and through the first turn. Riders engage Suzuki Holeshot Assist Control from a button on the left-side handlebar. The system can also be disengaged as well.

The second major change involves the RM-Z450’s suspension, Suzuki engineers have replaced the RM-Z450’s Showa Separate Function Fork with a 48mm Showa SFF Air Fork. Suzuki says that the SFF-Air was tested and proven by factory racer James Stewart last season, and it delivers a more progressive suspension feel and offers infinite adjustability in a package that shaves a lot of weight—nearly 2.5 pounds—over a conventional spring fork. Adjustments to the SFF-Air fork can be made easily via hand-held pump.

The RM-Z450’s fuel-injected, DOHC, 449cc four-stroke engine, which places its emphasis on strong low-end grunt and a stout mid-range. The 450’s lightweight, Keihin battery-less, electronic fuel injection system feature a progressive throttle linkage and 12-hole fuel injector designed to deliver optimum fuel atomization for smooth power delivery and precise throttle response to tackle the rigors of motocross and supercross.

Trackside tuning of the RM-Z450’s power character is a snap, thanks to a coupler system that offers three different ignition couplers designed to alter its power delivery. One coupler is set to stock specs, while a second module is set for a richer fuel setting and a third third is for a leaner setting. Swapping couplers is simply a matter of unplugging one and replacing it with another. The swap takes mere seconds to complete.

The RM-Z450 retains its five-speed transmission, but Suzuki says the transmission has been improved via precision gear matching for even better shifting feel. Cooling has also been improved via a more cooling system that transfers coolant between the radiators more efficiently. Other changes to the engine/transmission package are intended to make the RM-Z450 easier to start. They include a 30mm longer kickstarter, revised cam specs and an updated decompression system. The RM-Z450 exhaust muffler to meet strict AMA sound regulations.

Suzuki also took a look at the RM-Z’s twin-spar aluminum chassis and redesigned some of its frame members to net a 4-percent weight reduction while offering what Suzuki calls more balanced rigidity. The 48m SFF-Air fork is matched with a Showa Piggyback rear shock that features high/low-speed compression damping adjustability as well as rebound damping and spring preload adjustability.

RM-Z250
The 2015 RM-Z250 returns with the performance features that have made it a class standout in the past, including a light and compact 249cc, fuel-injected, DOHC, liquid-cooled four-stroke engine that is tuned for strong mid-range and top-end power and a twin-spar aluminum chassis designed to be light and rigid without being overly harsh on the track.
The RM-Z250 shares several features in common with its big sister, including a Keihin battery-less fuel-injection system with a 44mm throttle body, a progressive throttle linkage and a 16-bit computer for optimum throttle response and an electronic ignition system with swappable ECM modules. Another other unique change in 2013 included redesigned radiator fins and revised water hose routing to aid cooling. Renthal FatBars, Excel aluminum rims, and waved disc rotors are found on both the RM-Z four-strokes.

RM85
The Suzuki RM85 also returns for 2015 with essentially a graphic change. The RM-85 still boasts two-stroke power (yay!) in the form of a liquid-cooled two-stroke engine and six-speed. Disc brakes front and rear are designed provide ample stopping power, and the 17-inch front wheel and 14-inch rear have been determined to be the right size for basing berms or tackling the trails.

Pricing for all three 2015 models has not yet been set, but the complete line will be in Suzuki dealerships beginning in July. Suzuki has posted a substantial contingency program for all three machines and has also launched a new RM-Z/RM micro-site at http://www.suzukicycles.com/.