MXA’S 2006 RM-Z450 TEST

Ricky Carmichael put an exclamation point on the 2005 Suzuki RM-Z450’s maiden voyage when he took it to the AMA 250 National Championship. But history has conclusively proven that “win on Sunday, sell on Monday” is little more than an old wives’ tale. In a sophisticated market, the product’s charms far outweigh its racing promotion. Previous Ricky Carmichael championship seasons on the Kawasaki KX250 and Honda CR250 were met with a collective yawn from the buying public (in fact, sales dropped on those bikes the more Ricky won on them).

Thankfully, Suzuki doesn’t have to worry about that with the RM-Z450. As the flagship of Suzuki’s motocross lineup, it sold well in 2005. And Suzuki’s engineers didn’t sit pat for 2006. Although “all-new” can’t be applied to the ’06 RM-Z, there is hardly a piece on the RM-Z450 that didn’t get tweaked over the off season. How tweaked? That is what the MXA wrecking crew set out to discover.

 

Q: IS THE 2006 RM-Z450 IN ANY WAY RELATED TO THE 2006 KAWASAKI KX450F?

 

A: This is the most commonly asked question, and the answer is no. Although the Suzuki/Kawasaki alliance shared the RM-Z250/KX250F, no such deal exists for the 450cc version (and the 250cc agreement seems to be in tatters also).

 

Q: WHAT HAS BEEN CHANGED ON THE 2006 RM-Z450 ENGINE?

 

A: We’re impressed; impressed that Suzuki made any changes whatsoever to the RM-Z450 engine; impressed that Suzuki’s engineers would make changes to an engine that is barely a year old; and impressed by the impact of the mods. The 2005 RM-Z450 was a late release, not hitting the showrooms until January of 2005, while their red, blue and orange competitors had surfaced as early as August of 2004.

Here is a list of Suzuki’s 2006 engine changes:

(1) Head. Suzuki redesigned the cylinder head to accommodate a totally new exhaust port shape.

(2) Cam. There is a new grind on the RM-Z’s double-overhead, billet cams. The intake valve opens at 28 degrees (and closes at 84 degrees), while the exhaust is open at 68 degrees and closed at 46 degrees.

(3) Piston. Suzuki’s slipper-style piston gets a new three-piece oil ring with a chrome-nitride coating for improved sealing, reduced friction and longer life. There are also revised carburetor settings and revised ignition mapping.

(4) Gearbox. Although it remains a four-speed, the final drive ratio is higher, and the shift fork guide pins have been rounded for more accurate shifts.

 

Q: HOW DOES THE 2006 RM-Z450 RUN?

 

A: It’s faster, snappier and more responsive than it was 12 short months ago. Last year’s RM-Z450 was too passive off the bottom, especially for the RM-Z’s overly generous gearing choices. For ?06, the roll-on is much better (although the stock gearing is still too tall). The 2006 Suzuki RM-Z450 does its best work from idle to the middle. The top end is relatively flat. This is most noticeable when you try to rev the bike out to stretch a gear to the next turnit doesn’t pull through the top-end, but hangs and bangs.

 

Q: IS THE RM-Z450 FASTER THAN THE HONDA CRF450?

 

A:The short answer is no.

 

Q: WHAT IS THE LONG ANSWER?

 

A: It’s still no, but with caveats. It’s no secret that the Honda CRF450 produces an ideal powerbandenhanced even more by its concentrated five-speed gearbox. The CRF450 picks up quicker, carries its speed farther and is more furious in action. That said, the 2006 RM-Z450 is no slouch. Its powerband is very responsive. It is not as forceful as the CRF450, but it is less chuggy, doesn’t wind down under decell and has a deft touch in tricky situations. Test riders reported that they were never afraid to wick the RM-Z450 on. It responded to full throttle assaults with an obedient demeanor.

 

Q: WHAT IS THE RM-Z450’S GREATEST STRENGTH?

 

A: Usability. This isn’t a white-knuckle engine. There isn’t an inkling of John Force-style G forces. Instead, the RM-Z450 begs you to rattle its cage; wants you to wring it out; begs for you to abuse the throttle. In return, it delivers solid, manageable and effective thrust.

 

For owners of a 2005 RM-Z450, the ?06 model will definitely feel hopped up off the bottom. RM-Z aficionados who upgrade to the new bike will appreciate the extra snap at roll-on and grunt in the middle. Riders coming off of a CRF450 or YZ450F won’t think that the RM-Z450 is all that potent. It is less brawny than its red and blue brethren.

 

The RM-Z450 is perfect for riders who don’t need a quasar powerband. It probably isn’t potent enough in stock trim for a hard-core Pro, but it is baby bear’s porridgejust the right temperature for Vets, Novices, graduates from a 250F and two-stroke immigrants.

 

 

Q: WHAT IS THE 2006 SUZUKI RM-Z450’S GREATEST WEAKNESS?

 

A: Hands down, the four-speed gear ratios got every test rider’s vote as the biggest turnoff. They wanted the RM-Z geared down from the git-go. Switching from a 49- to a 50-tooth sprocket will punch up the power off idle and rush the RM-Z into its aggressive midrange.

 

Technically, gearing the RM-Z450 down brings all four gears in line with the ratios of last year’s four-speed YZ450F and this year’s five-speed CRF450. If you don’t gear it down, the RM-Z450 will have a taller first and second gear than its blue and red competitors (if we use the CRF’s second gear as comparable to the RM-Z’s first gearwhich it is).

 

The RM-Z is geared way too tall in first and second (probably to allow its fourth gear to be capable of the top speeds necessary for big tracks and trail riding).

 

Q: IS THIS THE SAME BIKE THAT RICKY CARMICHAEL RACED?

 

A: Yes and no, but more no than yes. Thanks to the AMA works bike exemption, Ricky was free to race a works bike during his triumphant 2005 season. And Team Suzuki took full advantage of the exemption, as Kawasaki will in 2006 with James Stewart’s KX450F. Ricky’s bike had a different frame, sand cast engine and special suspension components. Still and all, what Suzuki learned in building RC’s bike, they applied to the 2006 production bike. Need examples?

(1) Engine mods to the cam and cylinder head.

(2) Stiffer head tube (achieved by switching from a reinforced two-piece forging to a one-piece design).

(3) New swingarm with increased main beam height for less flex under a load.

(4) New rising-rate linkage for less bottoming.

(5) Stiffer shock spring mounted on a 2mm-shorter shock for better chassis balance.

(6) Increased high-speed rebound, more high-speed compression and less low-speed compression on the shock.

 

Q: HOW GOOD IS THE 2006 RM-Z450 SUSPENSION?

 

A: Showa has been very, very good to Suzuki in 2006. Every MXA test rider liked Suzuki’s take on Showa’s suspension components.

 

Forks: Suzuki opted for 47mm Showa Twin-Chamber forks. In most situations, MXA test riders prefer the 47mm fork legs to the stiffer and more rigid 49s. Every skill level, from Novice to National Pro, loved the RM-Z forks. The stock compression setting is ten clicks out. Faster riders set them on eight and slower riders went as far out as 12 clicks. We set the rebound on ten (the stock setting is eight clicks out).

 

Shock: We think that the Suzuki RM-Z450 has one of the better rear shocks in the class. Every MXA test rider loved this shockwithout exception. It goes straight through the nastiest stuff. It never kicks, hops or burps. Lines that rattled our teeth on other bikes, we assaulted on the 2006 RM-Z450.

 

Depending on your track, set the rebound on 15 clicks out, low-speed compression on ten and high-speed at two turns out.

 

Q: HOW DOES THE RM-Z450 HANDLE?

 

A: The MXA test crew loves the way the Suzuki RM-Z450 handles, but with one giant caveat. What is it? We hate the way it handles up until the exact moment when we get it properly balanced out.

The RM-Z450 can be the sharpest turning 450cc motocross bike ever made. But the setup is

all-important: get it right and you will be in seventh heavenget it wrong and you will be on Dante’s seventh level. The Suzuki engineers dialed in more oversteer than any other make. They achieved this with a very steep head anglealmost a full degree steeper than comparable machinery. And that steepness is evident at turn-in, where the RM-Z has a tendency to wag the bars before committing. The goal of the rider is to tone down the oversteer with a combination of fork height, race sag and compression damping. When you find the right numbers, the RM-Z knifes through berms and cuts inside of every four-stroke on the track.

 

This chassis rewards accuracy over stability. It requires intuitive knowledge to get the front and rear working in unison. It’s a little tricky to achieve, but we’d rather race on the sharp edge of the blade than on the dull side.

 

Q: WHAT IS THE BEST TOOL FOR DEALING WITH RM-Z450 OVERSTEER?

 

A: Fork height. A successful RM-Z450 rider has to be ready to slide his forks up and down in the clamps at a moment’s notice. Sliding the forks down in the triple clamps will relax the head angle, slow the steering down and make turn-in more controllable. Sliding them up will steepen the head angle, speed up the steering and make turn-in a thrill ride. We ran our forks a hair below the top indented line.

 

Q: WHAT DID WE HATE?

 

A: The hate list:

(1) Neutral: You wouldn’t think that the inability to find neutral would be a big deal. Wrong! Most of the time we found neutral with our hand instead of our foot. Irritating.

(2) Tire sizes. Suzuki went big on tire sizes. They have a wide 120/90 on the rear and an equally wide 90/100 on the front. We liked the way the 90/100 front feltit had a calming effect on the front endbut didn’t think the giant 120 rear footprint brought much to the party. We opted for a 110 in the rear. We also swapped the stock Bridgestones for Dunlops.

(3) Shifting. If you rev out the

RM-Z, the gearbox gets balky. It won’t shift under a full load with any regularity. No sweat, the RM-Z doesn’t like to be revved anyway. Short shift when possible.

(4) Gear ratios. Gear it down (by adding one tooth to the rear sprocket).

 

Q: WHAT DID WE LIKE?

 

A: The like list:

(1) Engine: The engine is sweet. It has a very tractable power delivery (it is so easy to ride that you don’t know how fast you are really going).

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

(3) Footpegs. Last year we whined that Suzuki should have spent the money they wasted on titanium footpegs on moving the hot start to the handlebars. For 2006, we get Ti pegs and a handlebar-mounted hot start.

(4) Clutch. It is ten times better than the RM250 clutch. It doesn’t buck when cold or lurch into gear.

 

Q: WHAT DO WE REALLY THINK?

 

A: Every bike has its perfect dance partnersomeone who has the perfect timing, steps and panache to make the most of the match up. For the RM-Z450, that partner is a hard-core two-stroke transplant. Suzuki has built the only four-stroke that has anything in common with a two-stroke. Unlike the runaway locomotive feel of most big thumpers, the Suzuki is light on its feet. Its powerband is quick and snappy. Its cornering is unsurpassed.

Is it a great four-stroke? No. But it is a great blending of the best of the two- and four-stroke worlds.

 

For more 2006 Bike Tests go to Top Ten Stories