2017 Suzuki RMX450Z

Introduction

• Suzuki gets back into the serious off-road game. Legally.

Suzuki is getting back into the off-road game in a tricky market segment. One that is bookended on one side by motocross competition machines on one side and by street legal dirt bikes on the other. The confusing part, for both the manufacturer and the customer is designing and selling exactly what a rider is looking for.  Where a bike winds up in is in one of three categories. Street legal, which requires a very complex set of requirements on both the manufacturer’s durability and warranty side as well as meeting a myriad of regulations. Making an EPA/CARB (or Green sticker) compliant off-road bike is slightly easier but it must still meet sound and emissions requirements that are almost as strict as on-road. The next, where a lot of manufacturers have landed, is in making a competition-only off-road race bike that is just like any motocross bike, for closed course competition use only.

Suzuki has chosen to go where there is a definite void in the market, the legal off-road bike. The only other truly modern bike in this category is the Yamaha WR450F, maybe the Honda CRF450X if you count carbureted bikes. For some riders having the ability to ride in green sticker areas (in California) or knowing they will be legal in areas like National Forests is important and not worth the hassle of converting a “street legal” dirt bike or risking riding a competition bike. Notebally KTM dropped the XC-W four-stroke in 2017 since it was so close to the EXC four-stroke. But some riders do not want anything with a license plate no matter if it is just a few extra lights and a gearing change away from being a dirt bike.

Changes

• This bike was all-new in 2010 and is back exactly the same save for an ECU change.

This bike was originally released in 2010 but immediately pulled from the lineup due to complications with its emissions certification. So it is back after seven years with one change to the ECU to make it compliant with current regulations. Looking back the RMX was using the RMZ450 motor for the most part with the additional parts and changes to make it electric starting and also housing a wide-ratio five-speed transmission. There are changes to the compression ratio, intake tract and cam profiles compared to the current RMZ but in reality this is the “older” RMZ motor in architecture as similar as it is from the outside.

The chassis sports the usual off-road suspects with an 18-inch rear wheel, a kickstand, an easy open airbox door and a coolant recovery tank. There are head and tail lights and an odometer/speedometer/timer. The muffler is built to keep the bike quiet for a long time yet it keeps the size and look of the racier RMZ. The RMX also comes with a six-month warranty which isn't too common on off-road bikes.

Power

• Chunky four-stroke power, after uncorking and with some fuel mapping help.
• Nicely spaced five speed transmission.
• Very quiet with the stock muffler.

The RMX comes restricted to the point it needed to be to pass stringent sound regulations. That means the opening of the throttle body is limited to about ⅓ of its range with a limiting screw. Additionally there is a snorkel inside the airbox to block noise and the muffler is very restricted compared to a competition muffler. In this form the bike is very quiet and runs just fine for a playbike in the 250cc range. Yes, it puts out playbike-like power, about ⅓ of what you’d expect just looking at it. Here the bike runs very lean, stalls easily and has a hard time pulling the taller gears if going up a hill. But you can ride it around wide open all the time and feel like a hero for stretching the throttle cable. Of note is that the bike has a hard time with cold temperatures and hates much altitude where it struggles to idle even with the idle adjust turned all the way in (out actually).

It was enough of that and we decided to use the bike for closed course competition use. That meant allowing the throttle to open fully and removing the airbox snorkle to start. Here the bike gains an impressive amount of power--only because we were so impressed with how little it made stock. Now the bike is still quiet and it runs much more like a Yamaha WR set up in a similar configuration. But the bike is still lean at idle and has a big step and inconsistent pull when going between the first ⅓ of throttle and the rest. If you ride the bike in higher RPMs and with big throttle openings it is fine. But in the bottom end the power is inconsistent and jerky. Overall power is in the strong running 250F category.

We tried both uncorking the stock muffler (which makes it loud to the point of being raspy) and adding an FMF Powercore 4 with a spark arrestor (still loud but not raspy) and the bike became in some ways better and some ways worse. The upper RPM and bigger throttle openings now gave the bike 450cc power, which we liked. But the step from the bottom to mid was more inconsistent and really had riders hating tight and technical riding where going between small and large throttle openings showed that the bike was suffering from fuel issues both rich and mostly lean. We decided to address this issue before complaining about it any more knowing that a rider who is interested in this bike would expect better.

We contacted JD Jetting and got an early version of the Power Surge 6x for the Suzuki. This unit (tested here http://dirtbiketest.com/product-tests/jd-jetting-power-surge-6x-fuel-injection-tuner) installed in about 30-minutes. This change made an instant impact on the way the bike ran. Right away the bike idled much more consistently and we were able to turn the idle adjuster back in and have some range with it. The step in the power between small and large throttle openings was now eliminated and this without messing with the setting on the tuner (also with an open exhaust). And it only took a few minutes to play with and fine tune the setting on the tuner to get the RMX running like a champ. The setting to alter the "accelerator pump" portion of the injection tuning had dramatic affect on the way the bike ran and would really boost or tame the engine character.

We expect most riders will be running the bike in a competition setting and we’ll comment on the engine performance in that setting. Now the chunky and more tractor-like power of the RMX comes out. It feels like it has a big piston and a longer stroke than most other modern four-strokes. You feel the power pulses and it feels like there is some flywheel mass helping things out. Roll-on is torquey and pretty smooth till the bike gets to the top-end where it jumps up in power and revs out plenty far. It does not rev as freely as most current bikes and it also has a bit more compression braking on deceleration. These are traits that some riders miss in current bikes especially in the FI era. Overall power is just a tad off the powerhouses in the 450cc class but few will complain because the RMX puts out more than most will ever really use.

For further testing we put the stock muffler (corked up to be quiet) back on the bike and with just a few button pushes on the JD tuner were able to have the bike ripping in a very stealthy mode. It was definitely down on power and throttle response at all throttle positions--but in reality a much easier to ride trail bike setting for sure. And it was not any slower on top speed so it is making power up there. We hit 92 MPH with both open and restricted mufflers.

We were getting right at 35MPG with the bike no matter how we rode it which allowed us about 45-55 miles before the light came on and it ran dry at 65 miles on a faster desert ride.

The RMX’s clutch pull is on the lighter side of average and the control was good for a cable activated system. We liked that the quick adjust was easy to use and could compensate for changes in performance when being abused. And the cooling system was up to the task of dealing with the abuse, yet we were always riding in cooler temperatures. The catch tank does its job!. Suzuki’s version of a wide-ratio transmission is more of a semi-wide-ratio gear box in our opinion. First is not super low and there are not any real gaps in the spread. The bike tops out just before getting on the rev limiter so fifth is fine. It is great for most racing speeds for sure and the power lends itself to long pulls between shifts. Shifting did not draw any complaints. The electric starter looks to be very strong and overbuilt in comparison to some.

Suspension

• Initially stiff and then a very active move through the stroke.
• Good bottoming resistance.
• Heavier riders liked the setting, lighter riders did not.

Suzuki uses Showa suspenders on the RMX with a conventional 47mm coil-spring front fork. The settings have been tuned by Suzuki for off-road and differ quite a bit from the current RMZ setup, which is now air-based. Right away a rider will get the impression the RMX is a stiffer setting and intended for more aggressive riding. This feeling is affected by a stiff chassis but we will get more into that in the handling section.

Overall there isn’t much to complain about in the suspension department with regards to the components--they are quality. The fork and shock are actually as good as forks and shocks have ever been. They are balanced and the fork and shock do work together.

The beginning of the stroke is on the stiff side for off-road and this holds the bike up and really helps the handling have a consistent feel. It also gives the rider more feel for the ground to the point that trail riders might feel the bike is too stiff if they are in the correct weight range. Heavier riders did not complain. You can tune some of it away with clicker settings but it becomes a trade-off. Especially since the RMX really likes to use the travel on bigger hits. Once moving the suspension has a softer feel and will absorb hits with minimal resistance and then at the very end of the stroke come in with a big spike of damping to resist bottoming way better than it feels like it should. So our issue was when softening up the initial it blew through the stroke too quick and too much. And the initial bump compliance took away from the RMX being comfortable. Yet the more aggressive you ride the bike the less and less a rider seems to care about the comfort and the suspension starts working. A few years ago this setting would have been way too stiff feeling, but this is the direction off-road race bikes have started to go.

You can easily take the RMX onto a track and it will do almost everything an RM will for most riders, save for two things. It bottoms much easier on mis-timed jump landings and will use a lot of the stroke on high-load jump takeoffs. But where it really works is in an off-road or GP race setting where you are pushing and less concerned about comfort and really needing the suspension to absorb bumps, roots and rocks without deflecting.

We feel with a little valving adjustments we could get the bike working better but we’d have to pick a direction for this bike. Either more racy with some additional mid-speed valving or for more comfort by taking away some initial compression valving and likely dropping a spring rate for an average weight rider. We ran the ride height between 100-107mm and found the bike was not as picky as some, especially because it never lost stability or turning unless it was way off.

Chassis - Handling

• Turns great, everywhere.
• Rigid chassis that transmits vibration and makes you feel the ground.
• Acts lighter than it is and the weight only comes around when you get on the power.

There is one standout trait of the Suzuki chassis and that is stiffness. The RMX is pure RMZ here and you feel it in every aspect of riding. Starting with vibration. We don’t think the motor vibrates any more than others but since it is held so tightly in a rigid frame the rider will feel it more. And the bike will even “walk” while idling on its side-stand.

This stiffness also amplifies the initial feel of the suspension more than it should. We carefully watched the suspension move on smaller bumps and chatter where a rider would notice it. It was exactly the same movement (to the eyes) as other bikes but the rider had a completely different feel. It is like you are running an extra 5 PSI on the tires if we were to describe it, but without the loss in tire grip. You feel the bumps mostly through the foot pegs and also in the bars.

So you may think we are just going to complain about the stiff chassis but it has some strong points too. The stability and predictability of the chassis is never in question. When pushing the bike and hitting bumps it goes straight and true. The turning and front end feel is planted and stable. When you hear, “nothing turns like a Suzuki” this is part of the equation. And for a bike that is weighing in at 270 pounds with a full tank (only 1.6-gallons) it acts way lighter than the scale says. Odd for a stiff bike. It can have its moments where the bike feels all of its 270-pounds but it was mostly in a planted and hooked up way, hard on the gas.

The steering has a very light feel especially for riders who judge the weight feel of a bike from the handlebars. When going side-to-side the bike also stays light, or at least very consistent, likely having less fuel up high contributes to this. And because the chassis is stiff, a rider can really feel what the front end is doing, there are no mysteries here. The same can be said for how the back of the bike is tracking and hooking up. Most riders said they could really feel the ground.

With the smaller tank it was no surprise the bike feels very thin to everyone, especially those used to a larger tank. The layout is seamless and dare we say very Honda like in a complementary way. The filter is easy to get to and not too tricky to change without tools even if it is a tight fit. Suzuki uses a lot of smaller fasteners on some parts but as long as you take care with them (seat bolts to be specific) there isn’t an issue. The plastic skid plate does a good job on the smaller stuff but we cracked the ignition cover on a rock (through the skid plate). The plate took a major damage hit and reduced it into minor damage. The brakes were average, which is excellent these days. Some laughed at the steel kickstand saying it may have been a leftover part off of the original 1977 Suzuki PE250 yet it did everything asked of it.

We have to point out that the RMX’s odometer computer is a pretty nice item with the usual functions including average speed and an adjustable trip meter in sport mode. Then there is the tires, Dunlop's 756 rear and 742FA front and we forgot how much we liked these tires.

One thing that worried us was the use of the on/off button. When on it leaves the headlight and taillight on and will drain the battery in about 15 minutes so that the bike will not start with the electric starter. It is easy for some to forget about. Luckily the bike will kick-start even with a dead battery unlike some others. Or others with no back-up system in place.

Conclusion

• Another viable choice for the right rider.
• Be prepared to tune the bike into a winner.

So where does this Suzuki RMX450Z fit into the picture? Well nicely if you are a Suzuki dealer as it fills a void for having an off-road compliant sound and emission legal bike on the showroom floor. There is only the Yamaha WR450F and Honda CRF450X available in this configuration since KTM and other Euro brands have decided to go full competition or street legal. For some riders this is an important position for a bike to fit into.

We were not impressed with the bike in the stock motor configuration so we tested it in a competition setting as a racing bike. Here the bike does everything it should but it takes some work to get to this point. There is a lot of competition from other bikes and brands in this arena but the RMX has some traits that are clear and defined. If you like more classic Thumper power and a stiff chassis then the RMX has a lot to offer. It is predictable and confidence inspiring especially when pushing it hard in racing conditions. Plus it turns like a Suzuki.