MXA RACE TEST: The New 2009 Suzuki RM-Z450; Suspension Settings, Jetting Specs, Likes & Dislikes, Plus Much More

February 28, 2009
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INSIDE THE NEW 2009 SUZUKI RM-Z450



    Imagine that you poured your heart and soul into building the most advanced motocross bike ever offered to the public. It was going to be the first motocross bike from a major manufacturer to come with electronic fuel injection. Best of all, it was a full year ahead of the competition in terms of technology. Not only was your company backing it with a massive contingency program, but they were ready to spend millions on advertising, racing, promotion and marketing.

    Then, a glitch appears in one cast part. Engines start breaking before the bike is delivered to the showrooms. It is a disaster of epic proportions. Bikes languish on the docks, while engineers rush to find a fix for the problem. Weeks drag into months before a solution can be found. You miss the fall, winter and spring selling seasons. The showrooms are empty, as are your coffers.

    That is the dramatic story of what Suzuki went through with the 2008 Suzuki RM-Z450. With 2008’s high hopes down the drain, Suzuki regrouped for 2009. Unfortunately, their technological lead vanished in the 12 month delay. But all is not lost. The teething problems have been fixed, and the bike is ready for sale.

    The MXA wrecking crew wanted to find out what the world was missing.

Q: WHAT’S NEW IN THE 2009 SUZUKI RM-Z450 ENGINE?

A: There is only one change on the RM-Z450 engine from 2008 to 2009, but it is very important. The right side engine case has been reinforced with additional ribs and thicker wall diameters. It was a failure of this engine case that caused the 2008 RM-Z450 to be delayed for months (and eventually it was subject to a recall once the bike did arrive).

Q: IS SUZUKI’S FUEL INJECTION AS GOOD AS THE EFI ON THE CRF AND KX-F?

A: Yes. In a way, Suzuki paved the way for Kawasaki and Honda. Although there are minor differences between the three systems, the similarities dominate 99 percent of the design. What are the differences?
 

    (1) Suzuki uses a 43mm throttle body (as does Kawasaki). The Honda CRF450’s throttle body is 50mm.

    (2) Honda and Kawasaki both offer optional software and plug-in programmers for around $350 that allow the fuel injection system to be altered. Suzuki does not, although Yoshimura offers an aftermarket ECU programmer.

    (3) All three bikes have their fuel pumps in the gas tanks, but Honda and Kawasaki use rotationally molded plastic gas tanks, while Suzuki uses an aluminum tank. Fuel capacity on the Suzuki is 1.6 gallons (1.8 on the KX450F and 1.5 on the CRF450).

Q: DOES THE RM-Z450’S EFI NEED RACE GAS?

A: No. In our opinion, race gas is not necessary. None of the three fuel-injected bikes need high-octane gas.

Q: WHAT ABOUT THE JETTING?

A: There is no jetting. The only thing a rider has control over is a 50-click idle adjustment screw that changes the air mixture slightly (it doubles as the choke knob). It is set at a much higher idle than a carburated bike.

Q: DOES THE RM-Z450’S EFI SYSTEM SUFFER FROM FLAME-OUT?

A: Yes, but the solution can be found at the choke knob. Flame-out is when the engine quits suddenly at low rpm. All three fuel-injected bikes have flame-out issues (although the KX450F is less susceptible, thanks to its heavier moment of inertia). The easiest fix for flame-out is to turn the EFI’s idle screw two or three clicks counterclockwise. This will pick up the idle speed.

Q: HOW MUCH HORSEPOWER DOES THE 2009 SUZUKI RM-Z450 MAKE?

A: It makes 50.08 horsepower. How does that compare to other 450’s? On a positive note, it is not the lowest peak horsepower of 2009 (Yamaha takes that dubious honor), but the RM-Z450 is nowhere near the top of the heap. The KTM 450SXF makes 53.98 horsepower, the KX450F makes 52.33 horsepower and the CRF450 makes a marginally better 50.25 horsepower.

    In simplest terms, the KTM is very close to four horsepower better than the RM-Z450.

Q: WHAT IS THE BEST PART OF THE 2009 RM-Z450’S POWERBAND?

A: Throttle response. All three fuel-injected bikes are amazingly good off idle and through the low-to-mid transition. They start operating about 500 rpm before the carburated bikes and with about five more horsepower at initiation. The throttle response is awesome on all three, but different. The CRF450 is jumpy at low rpm, while the KX450F is torquey. If you compare the three fuel-injected bikes to the three bears, the RM-Z450 is Baby Bear’s porridge just the right mix of instantaneous response and horsepower.



Q: WHAT IS THE WORST PART OF THE 2009 RM-Z450’S POWERBAND?

A: The 2009 RM-Z450 signs off too soon. The horsepower peaks at 8900 rpm (50.08 horsepower), and by 10,000 rpm the rev limiter begins to kick in (and it is a hard rev limiter, one that shuts the power off immediately, as opposed to the soft rev limiters on the SXF, KX-F, CRF and YZ-F). Power builds quickly from off idle to 8000 rpm, then flattens out until it reaches 8900 rpm, where it begins to descend to its 10,000 rpm cutoff. This kind of powerband doesn’t allow you to stretch one gear to the next corner. It demands that you shift, and shift now. There is no over-rev to work with.

Q: IS THE 2009 RM-Z450 FASTER THAN THE 2008 RM-Z450?
 
A: No. It’s a clone, with the identical horsepower, torque, powerband and sensations.

Q: WHAT IS THE MOST ACCURATE ASSESSMENT OF THE 2009 RM-Z450 POWERBAND?

A: This is a very good engine if you live within its limitations. It doesn’t make a ton of horsepower, and what horsepower it does make happens in the first half of the powerband, so it is important to ride the 2009 RM-Z450 as though it were an RM-Z350. Think of it as a very powerful little bike, not an underpowered big bike. Ride it hard, shift it often and dive to the inside whenever possible.

Q: HAS ANYTHING ELSE BEEN CHANGED FROM 2008 TO 2009?

A: The engine cases, yellow front number plate, new seat cover and BNG (Bold New Graphics) are the only differences between a 2009 and 2008 RM-Z450.

   Theoretically, Suzuki had no need to build a completely new RM-Z450 for 2009. It is, for all intents and purposes, a brand-new bike. Very few 2008 models ever saw the light of day and, even then, they went on sale about eight months after the 2008 green, red, blue and orange bikes.

Q: HOW DOES THE 2009 RM-Z450 HANDLE?

A: Great. The RM-Z450 is the best handling 450cc motocross bike on the track today. It has traded in any illusion of all-around handling in favor of quickness in the tight stuff. It can turn circles around the competition. The MXA wrecking crew loves Suzuki’s handling choices. In a weird way, Suzuki’s four-strokes handle like two-strokes. While many 450cc bikes handle like runaway trains, Suzuki has gone a full degree steeper on the head angle and much more agile on the response scale. Matched against the CRF, YZ-F, KX-F and SXF, the Suzuki RM-Z feels like a 250F.

   The 2009 RM-Z450 feels slim, trim and svelte. If you closed your eyes, you would never guess that you were on a 450cc motocross bike.


Q: WHAT IS THE BEST WAY TO MAXIMIZE THE RM-Z450’S HANDLING PROWESS?

A: Learn to work with the fork height and race sag to get the most out of the razor-sharp chassis. One of the downsides of building an ultra-steep and ultra-quick handling bike is that it doesn’t take much to push it over the edge. Here are the keys to staying on the sharp edge of the knife.

    (1) If you want it to turn sharper, slide the forks up in the triple clamps. The farther up you go, the steeper the head angle will become. On the opposite end of the bike, the less race sag you put into the rear shock, the steeper the head angle will become. The Suzuki RM-Z450 already has a 1.2-degree steeper head angle than any other bike. If you make it steeper, the bike will turn, but you also run the risk of making it oversteer.

    (2) If you want it to be more stable, sliding the forks down in the clamps will slacken the head angle. Most MXA test riders like to mellow out the Suzuki geometry on fast, high-speed tracks. Longer forks or more sag can have a calming effect on the chassis by bringing the head angle back closer to the numbers of the other 450s.



Q: HOW IS THE SUSPENSION ON THE 2009 RM-Z450?

A: The forks have issues. They had setup problems last year and, since they are the exact same forks as in 2008, they suffer from the same woes. What is the problem? The Showa forks are undersprung. Way undersprung. Unless you weigh under 150 pounds, you will bottom (and the forks will feel too stiff?even though they are too soft). Our best advice is to go to stiffer fork springs. We changed the stock 0.47s to 0.49s. Once you have the correct springs, you can raise and lower the oil height to meter the midstroke.

Q: WHAT WAS OUR BEST FORK SETTING?
 
A: For hardcore racing, these are MXA’s recommended 2009 Suzuki RM-Z450 fork settings:
    Spring rate: 0.49 kg/mm (0.47 stock)
    Oil height: 370cc
    Compression: 11 clicks out
    Rebound: 11 clicks out
    Fork leg height: 5mm up
    Notes: On smooth tracks, with a light rider or in the hands of a very slow rider, the stock forks are at their best. But, even then, the rider would have to turn the clickers as far in as possible.

Q: WHAT WAS OUR BEST SHOCK SETTING?
 
A: Amazingly, we could live with the stock shock spring (although there are caveats for heavy or fast
riders). For hardcore racing, these are MXA’s recommended 2009 Suzuki RM-Z450 shock settings:
    Spring rate: 5.6 kg/mm
    Race sag: 100mm
    High-compression: Two turns out
    Low-compression: Eight clicks out
    Rebound: Seven clicks out
    Notes: Heavier or faster riders should go to a 5.8 kg/mm shock spring.

Q: HOW MUCH DOES IT COST?

A: $7499. For comparison, the suggested retail price of the YZ450F is $7399, KX450F $7549, KTM 450SXF $7998 and CRF450 $7599.

Q: WHAT DID WE HATE?

A: The hate list:

    (1) Shift lever. The MXA test crew has never missed as many shifts on a Suzuki before. If you rushed a shift, you could end up in neutral. Why? The bend of the shift lever is so obtrusive that the odd shape of the shift lever hampers getting all of your foot under it. You will learn, by experience, to avoid hitting the bend in the lever.

    (2) Axle blocks. Don’t trust the chain adjustment marks.

    (3) Top-end. MXA test riders learned to make the most of the crisp low-to-mid powerband, because the power is soft on the top and comes up against the most obnoxious rev limiter we have ever felt.

    (4) Rear brake. We smoked it.

    (5) Forks. We are beginning to believe that Showa has lost their way. The RM-Z450 forks are way too soft, which makes them feel very harsh as they reach midstroke. Worst of all, they bottom harshly.

    (6) Bolts. Suzuki’s bolts are slightly undersized. How do we know? Every time we put an 8mm T-handle on a Suzuki seat or side panel bolt, it slips off. Suzuki needs to invest in better hardware.
 
Q: WHAT DID WE LIKE?
 
A: The like list:

    (1) Starting. It was easier than Suzuki said it would be.

    (2) Handlebars. You gotta love the Renthal FatBars.

    (3) Handling. It is razor sharp. It won’t be everybody’s cup of tea, but it’s uniquely different from every other 450 four-stroke.

    (4) Footpegs. The footpegs have “positive draft.” What is positive draft? It defines a footpeg shape where the opening at the bottom of the pegs is larger than at the top?which means that mud falls out instead of sticking.

    (5) Sound. Under the 94dB FIM limits that went into effect at the start of the 2009 Supercross series, the 2009 Suzuki RM-Z450 passes easily. That doesn’t mean that it makes under 94 decibels, only that its 95.5dB muffler is bureaucratically legal for 2009.

Q: WHAT DO WE REALLY THINK?

A: Here is MXA’s wish list for the 2009 RM-Z450. We wish it had stiffer fork springs and more fluid damping. We wish it shifted better. We wish it had more over-rev, horsepower and a softer rev limiter. We wish Suzuki had taken the time to fix the problem areas of the 2008 (instead of just bolting on a new right center case). Does that sound like too much for Santa or the Easter Bunny to bring to us? Luckily, we have the option of sending the forks out, taking our time between shifts, and buying an aftermarket pipe. It is possible in modern motocross to pony up for most missing attributes.
   
    One thing that money can’t buy, no matter how much is in the bank, is great handling. Only one bike is the best handling, and that bike is the 2009 Suzuki RM-Z450.


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