First Impression – 2005 Suzuki RM-Z450



For Suzuki fans, the four-stroke RM-Z450 is, without a doubt, the most exciting new bike of the 2005 model year. All new from the ground up, a preproduction version of the bike has been campaigned overseas in the World Championship GP Series and the All Japan National MX Championships for over a year now, and has made the mouths of valve-and-cam fans everywhere water in anticipation. When Suzuki first unveiled the RM-Z450 at its annual dealer show in June, no one expected the multiple production delays it eventually encountered. After all was said and done, the optimistic September, 2004 delivery date had turned into mid-January, 2005.
AT LAST!
The most exciting feature of the new machine is the aluminum frame, as Suzuki becomes the third manufacturer to produce an aluminum-framed motocross bike. (Well, fourth, if you count the ill-fated “Bike of the Year” Cannondale.) While Yamaha’s engineers chose to retain traditional frame design on its new aluminum YZ lineup, there is no denying the similarities between the new Suzuki frame and Honda’s fourth-generation twin-spar chassis. Internet rumors abounded about the Suzuki’s late release, the most common being a patent infringement on Honda’s design, but that’s neither here nor there now, as the bike is finally here. (And for the record, it was late changes in the preproduction testing process that caused the delay.)
The four-speed, four-valve, double-overhead-cam powerplant is quite compact; in fact, the points between the swingarm pivot and top of the spark plug do not differ that greatly from the two-stroke RM250 motor. Suzuki claims that the RM-Z450 is, without a doubt, the most powerful motocross engine it has ever produced.
Suzuki engineers and test riders set out to develop a big-bore thumper that would maintain typical RM motocross bike-handling traits, even though the motor and chassis material and design were radically different. Still, the RM-Z’s frame geometry and weight bias are indeed relatively close to those of its two-stroke brethren.
Showa suspension components grace both ends of the bike; a 47mm cartridge-type fork and a fully-adjustable shock with a 50mm body and 18mm shaft handle the bumps and jumps. Familiar quality components such as Nissin brakes, Excel wheels and a Renthal Fatbar round out the package that we’re sure you’re tired of reading technical details about, so let’s get on with the test already! (Visit www.transworldmx.com for a full technical debriefing.)

HOW IS IT ON THE TRACK?
After our photo model Sebsatien Tortelli finished whipping the bike around for our cameras, we were anxious to throw a leg over the new yellow thumper and managed to get three solid days of riding in before this feature had to go to press.
So, you’re wondering: “Was it worth the wait?” In a nutshell: yes! The Suzuki RM-Z450 is an excellent motorcycle, and in its first year of production it is absolutely, positively 100% competitive with the established offerings from Honda, KTM and Yamaha. In the time we’ve spent on the machine thus far, we’ve come to love it for its power, manageability, handling characteristics, suspension action and overall fit and finish.
We’ll start with the motor first, since questions about the bike’s power were the ones we fielded the most. The RM-Z engine is very user friendly, but don’t for a second think that is our nice way of saying it is slow! With a super-linear powerband, the RM-Z cranks out a confidence-inspiring spread of power that is good from zero rpm on up to about 11,000. Low-end power is nice and strong and rolls on smoothly as the throttle is applied with no hiccups, coughs or hesitation. (On that note, we must mention that for our sea-level locale, the RM-Z came jetted spot-on.) Power builds steadily and gradually, never coming on suddenly with a big hit, but instead producing a traction-grabbing surge that makes the Suzuki the easiest-to-ride thumper in its class. While the Honda and Yamaha ve more of a hit in the middle that can tire lesser riders out, the Suzuki-like the KTM 450SX-has a very controllable wealth of horsepower. One of the things we admire most about the RM-Z motor is its adaptability, as it is very effective when short-shifted and kept in the sweet spot, but just as at home being revved out before each shift. The Suzuki pulls long and far in each gear, allowing you to shift less if you so desire. Of all the 450cc four-stroke power plants around, this may be the most adaptable to the widest range of rider abilities and styles.
The gears of the four-speed transmission are spaced nicely, and we were able to ride most tracks in second and third gear, no problem. None of the courses we tested on were wide-open enough to spend any amount of time in fourth, but the transmission never left us wishing for more or less in any of the conditions we encountered. Shifting action is typical Suzuki and buttery smooth, and the clutch pull is light at the lever with good feel. Even under heavy (and incorrect) abuse, the clutch never faded, squealed or lost its play.
Firing up the RM-Z is usually a one or two-kick affair, even when hot. The kickstart lever has good leverage and doesn’t require any sort of above-average leg muscles to get the beast fired up. Thankfully, the automatic compression allows you to kick away without worrying about top-dead-center. The RM-Z’s biggest fault, however, is that there is no handlebar-mounted hot start lever. Instead, a red button mounted on the side of the carburetor must be pulled out, and older Yamaha YZF pilots all know how hard that is to do with any amount of dexterity in race situations. Suzuki reports that a rival manufacturer’s patent on a handlebar-mounted hot start kept them from equipping the RM-Z with one, but that doesn’t offer much solace when every other four-stroke motocrosser produced today has one. Plan on buying an aftermarket conversion kit like the excellent Dubach Racing Development unit. That is, unless, you are a rider who never stalls the motor…
Ergonomically speaking, the Suzuki is a very comfortable bike with a thin feel between your legs and a nice, open rider compartment that doesn’t feel too big or too small. On the track, the bike has a light feel and a very neutral weight bias, front to rear; even more so than the front-end light RM250. The bike tracks superbly, as there is a substantial amount of weight placed on the front wheel, and a high traction level is the result. This could quite possibly be the best-cornering bike we’ve ever tested, two-stroke or four. Say what? Yes, that’s right: the RM-Z450 inspires nothing but confidence in all sorts of turns, but especially tight, rutted corners that most big-bore four strokes suffer in. Testers found that the RM-Z was very easy to get in and out of tight inside ruts on, as its combination of good balance and smooth power delivery made it a breeze to maintain control. In low-speed situations where other big thumpers feel tall and heavy, the Suzuki has a low, squatty feel that we love. Under hard acceleration, the RM-Z-like its two-stroke RM250 brother-is a superb slider. Powering through acceleration chop with the rear end continuing to slide is a smooth, predictable affair, as the bike never swaps or kicks unexpectedly.
Suspension action on both ends is superb; though we did find that as delivered the shock’s rebound settings were a little speedy. Set at 17 clicks out, we found that the back end felt a little too active and tended to send us flying through the air nose down, especially over steep-faced jumps. Going in on the shock’s rebound adjuster about five clicks corrected the problem. Suzuki recommends running 104mm of shock sag, but we found that you could run the back end as low as 106mm without sacrificing the bike’s cornering abilities. As is the case with most bikes we’ve tested, the suspension is designed with the average rider in mind and should suit most riders with some fine-tuning. As we logged more and more time on the RM-Z, we found ourselves adding additional compression damping up front. Faster or heavier riders may wish for stiffer springs or a higher oil level.
Still, the front and rear suspension components are well balanced and do a great job of soaking up all of the track’s imperfections. Plush in the small stuff, progressive in the middle of the stroke and firm in big-hit situations, the Showa components keep the RM-Z straight and in control. We were able to adjust the bike to suit a wide range of riders, from novice to pro.
During the time we’ve spent with the bike, one of the strangest things we’ve encountered is the way in which you must service the air filter. After removing the seat and struggling to get the air filter and cage out through the top of the subframe, we realized that accessing the system through the left side of the airbox is the only option. Though it seems unorthodox for those of us who have never ridden KTMs, removing and installing the air filter through the side of the bike isn’t as odd as it initially seems. Removing the left side panel is actually easier than taking the whole seat assembly off, even though the same number of bolts are involved.
All in all, we are thus far quite pleased with the performance of the Suzuki RM-Z450. Though it is not the fastest bike in its class as far as brute power is concerned, it is plenty fast enough and one of the easiest-to-manage full-sized bikes. With great suspension, superb handling characteristics and a solid powerplant, it seems Suzuki has succeeded in scoring a home run in its first at-bat in the big-bore thumper category.
some fine-tuning. As we logged more and more time on the RM-Z, we found ourselves adding additional compression damping up front. Faster or heavier riders may wish for stiffer springs or a higher oil level.
Still, the front and rear suspension components are well balanced and do a great job of soaking up all of the track’s imperfections. Plush in the small stuff, progressive in the middle of the stroke and firm in big-hit situations, the Showa components keep the RM-Z straight and in control. We were able to adjust the bike to suit a wide range of riders, from novice to pro.
During the time we’ve spent with the bike, one of the strangest things we’ve encountered is the way in which you must service the air filter. After removing the seat and struggling to get the air filter and cage out through the top of the subframe, we realized that accessing the system through the left side of the airbox is the only option. Though it seems unorthodox for those of us who have never ridden KTMs, removing and installing the air filter through the side of the bike isn’t as odd as it initially seems. Removing the left side panel is actually easier than taking the whole seat assembly off, even though the same number of bolts are involved.
All in all, we are thus far quite pleased with the performance of the Suzuki RM-Z450. Though it is not the fastest bike in its class as far as brute power is concerned, it is plenty fast enough and one of the easiest-to-manage full-sized bikes. With great suspension, superb handling characteristics and a solid powerplant, it seems Suzuki has succeeded in scoring a home run in its first at-bat in the big-bore thumper category.