Cycle New’s Jason Abbott gave the new air-fork-equipped 2015 Suzuki RM-Z450 a two-day workout at Zaca Station and Castillo Ranch. Photography by Adam Campbell.

We recently headed to two of California’s finest motocross tracks—Zaca Station and Castillo Ranch—for Suzuki’s two-day launch of the 2015 RM-Z450. Although the new Suzook doesn’t look much different than last year’s RM-Z450, that doesn’t mean it hasn’t changed. It has!

We have a somewhat love/hate relationship with the 2014 RM-Z450. The bike is the best-turning 450 machine out there and it has a powerful yet rider friendly engine that is one of our favorites to unleash. Take the RM-Z450 to a track with tight turns and jumps and we're in love with it, but on faster and rougher track, like Glen Helen Raceway on a busy practice day, the romance goes away; it feels like a completely different motorcycle. One that beats you up. Our big complaints with the 2013 and 2014 RM-Z450s are their rigid-feeling front end and their unpredictable handling on rough and nasty tracks. The shock, however, has always performed well but, for us, not the SFF Showa spring fork, so we were excited when we heard about the ‘15’s new 49mm Showa SFF TAC-Air fork, which is very similar in design to the new air fork on the 2015 Kawasaki KX450F.

Suzuki didn’t tinker much with the RM-Z450’s motor. Might as well leave good enough alone.

Suzuki says that the new fork weighs 2.5 pounds lighter than the previous spring fork and is much stronger yet provides just the right amount of rigidity. With compression and rebound clickers on the left side and the triple air chambers on the right side, the new Showa fork is not only lighter and stronger, but perhaps more importantly, is far more adjustable. Also, with the TAC design, you won’t see a rise in air pressure inside the chambers when you see a rise in air temperature outside, which is a problem with the earlier air forks found on the Honda CRF450R and KX450F. The TAC design basically eliminates the problem of inconsistent performance.

Suzuki didn’t stop at the fork. It also updated the RM-Z’s aluminum frame. Look closely and you’ll see the redesigned downtube and the reshaped mainframe inner ribs. The result? Increased and decreased rigidity in key areas, and a four-percent reduction in weight.

The 2015 RM-Z450 joins the air-fork wars with its own 49mm Showa SFF TAC-Air fork.

In the power department, Suzuki didn’t need to do much because everyone was already happy with the RM-Z’s mill, but the 449cc four-stroke liquid-cooled DOHC four-valve engine still received a few minor updates. The ECU was remapped to refine what we feel is already a solid power delivery. The piston pin gets a diamond-like carbon (DLC) surface treatment for less friction and increased durability, and the lightweight aluminum cylinder features a SCEM coating (Suzuki Composite Electrochemical Material) for increased durability and more efficient heat transfer.

To making starting a little easier (a slight problem with the previous RM-Z450s), it now has a longer kick-start lever, a redesigned kick-drive gear, a relocated kick idle gear, a newly added breather gear and a redesigned decompression system.

For more precise shifting there’s a revised gearshift cam, and precision machining was used to match the gears a little better in the RM-Z’s five-speed transmission. 

Engine cooling is now more efficient. A redesigned water pump cover and a direct-connect hose increases flow by 16 percent, which is significant. A cooler-running engine maintains power longer. There is also a new Y-shaped main hose (instead of T) for a more equal flow between the left and right radiators.

To help reduce noise, the muffler, which looks the same out the outside as it did before, has a new inner-pipe.

Updates to the chassis gives the Suzuki a more forgiving ride.

A welcomed addition to the RM-Z450 is the new Suzuki Holeshot Assist Control (S-HAC), which is operated by a button on the handlebar. Unlike Kawasaki’s similar Launch Control Mode, which has one setting, the RM-Z’s S-HAC gives you two launch modes to choose from: one, Mode A, for concrete (slippery) pads and one, Mode B, for dirt (good traction) pads. For Mode A, hold the button for about a half second, for Mode B, hold it down for about a full second.

Basically, for 2015, Suzuki chose to make performances changes over cosmetic changes, so the RM-Z wears the same clothes as it did before but with some minor graphic changes.

The new RM-Z450 carries an MSRP of $8749, which is an increase of only about $50, which is amazing when you consider the new forks, which are much different than what James Stewart is using on his works bike. Suzuki also offers a lucrative contingency program for its big-bore motocrosser. You can get all the details at www.suzukicycles.com.

GIVING IT A RIDE

We can say now that our love/hate relationship with the RM-Z450 is now pretty much all love. What a difference! The new fork is a huge improvement over the previous RM-Z450, and all of the changes they made to the chassis seem to be all of the right ones!

Right from the get-go, the 2015 RM-Z450 has a much-improved feel on the track, which has a lot to do with the new fork. Fork action is now more compliant and has better absorption than before, and the chassis doesn’t quite feel as rigid. The bike just doesn’t beat you up as much as the previous two RM-Z450 models did, though it is still just as agile and easy to throw around.

As good as the fork is right out of the crate, however, we made some changes to it over our first two days on the bike.

Not surprisingly, we are impressed with the RM-Z’s new air forks. It’s just what the doctor ordered.

While the fork action is quite good via the stock settings, we increased the inner chamber 10 pounds to help hold the front end up a little more in the stroke, to reduce brake diving, and to give mid-stroke a firmer feel. To maintain the bike’s overall balance with these new settings, we increased pressure in the balance chamber a bit. Just these few tweaks alone put a real smile on our faces. We can only imagine what we can do with this fork with more time. We feel we’re just scratching the surface.

We’ve never had much to complain about when it comes to the RM-Z’s rear suspension, and we still don’t. Out back we were fairly happy with the stock settings with the sag at the seemingly standard 105mm recommendation. Once we got the fork dialed in we slowed down the rebound damping by two clicks to calm the rear end a bit and to give the bike a more stable feel. Overall action of the rear end is again impressive and is one of the better performing production shocks out there.

Turning has always been a treat on the RM-Z and we are happy to report that it still is—nothing has changed. When it comes to the turns, going inside or outside, or through the ruts or berms, it doesn’t matter with the RM-Z; it handles them all extremely well.

The updated fork and changes to the frame bumped up our confidence when entering the corner, too, as the bike seems to hold its ground better over the braking bumps. Stability, at both high and low speeds, is noticeably improved. You will notice it, too.

Suzuki gave its engineers a choice: Make performance changes or cosmetic changes to the 2015 RM-Z450. As you can see, they went with the performance changes.

The ‘Zook’s front brake could use some help. After riding the new CRF450R and KX450F that both got over-sized front-brake rotors for 2015, the Suzuki’s front brake now seems a little weak in comparison. The bite just isn’t quite there—evidently, our standards when it comes to front brakes have risen a bit.

As for the motor, not too much new to report here. It feels very similar to last year’s mill, but the tweaks to the ECU seems to have smoothed things out a bit right off the bottom and added a bit more pizazz in the middle of the powerband. Top-end and over-rev feel the same—decent—but the meat and potatoes of this motor is still from bottom to mid and a little beyond. Don’t worry, the RM-Z is still plenty fast on top, but we feel that the RM-Z450 performs best when you short-shift it a bit and take advantage of its outstanding bottom-to-mid pull.

This bike does seem to take a little less effort to start, and we liked the new launch control. It’s simple to operate and really makes a difference on slick surfaces, but we haven’t had the chance to try it out on a concrete pad yet. With a less aggressive hit (Mode A), it’s easier to get the power to the ground for smoother and more controllable launches. Again, we applaud the addition.

We found the new muffler to be slightly quieter. Suzuki assured us that the quieter muffler does not rob power or performance.

We’re now in love with the RM-Z450 again.

As always, the RM-Z is comfortable in the seat. It feels slim between your legs and is easy to move around on, and we still like the tapered aluminum handlebars.

After just two days on the bike, it’s easy to conclude that the 2015 RM-Z450 is a much-improved motorcycle. Suzuki kept what we already love about the RM-Z450—its motor, turning prowess, ergos, maneuvability—and improved everything we didn’t like about it—forks and overly rigid chassis. Yes, it certainly could use a fresh new look, but for now, we’ll gladly accept the performance changes the Suzuki got over a change of plastic. Maybe next year, though. But we are, so far, happy with what we see—or should we say, don’t see—when it comes to the 2015 Suzuki RM-Z450.

 

By Jason Abbott

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