The middleweights are the supersports of the trails. They feature terrain-eating suspensions, the sharpest handling and lightweight performance. They have willing engines that respond to a driver’s wish to get to the next corner quickly. For the 120 hp middleweights, performance is above all else. Reporting on them accurately is a job we don’t take lightly, so we’re thorough.

The middleweight performance class is on the cutting edge of development. It’s an important class for each manufacturer, the ultimate street fight. This year there are two machines new to the arena. The most newsworthy 2010 machine, the Polaris Rush, is engineered to master terrain. Ski-Doo dropped another MX Z X-RS package into its latest model lineup fresh from its race department. We also included two returning but updated models, stamped with build dates for the 2010 model year, the Yamaha Nytro RTX and an Arctic Cat F6 Sno Pro, to see if the latest and greatest are outpacing models with which we’re already familiar.

We couldn’t wait to bestow 120 hp class champion status to a 2010 sled. To ensure one of the new sleds is worthy of winning our most prestigious shootout of the year, we queued the defending champion – the Ski-Doo MX Z 600 E-TEC X, a machine that was relatively unchanged from 2009 except for its clothing.

Snow Goer put this reinvigorated portfolio of machines – each with its own character – through two days of testing at our annual Rode Reports event. The trails in the Grand Lake, Colorado, area included stutter bumps, huge craters, G-bumps, sweeping trails, tight woods, ascents and descents, switchbacks and speedy straights. Five different riders conquered it all with each of these sleds to bring you the most thorough, unbiased — and surprising, perhaps — report.


Yamaha FX Nytro RTX – The Returning Powerhouse

Yamaha’s FX Nytro RTX dominated the engine category in our 600-class test last year (December 2008), and once again for 2010 no other machine here has the torque and acceleration of the Genesis 130Fi engine. Yes, it has a power advantage and is packing more heat than the rest of the machines here.

While it’s a 120 hp test grouping, Yamaha lumps this torquey, EFI four-stroke into a 130 hp category – and it’s cheating, in a good way. We’ve seen enough dyno reports to know this engine is closer to 135 hp. The sweet four-stroke engine sound is just an added bonus to the over-delivered power.


With the change in model year designation came a short list of appearance, durability and comfort updates. The most noticeable is the new tapered tunnel. Yamaha said it helps evacuate snow and puts riders into a better attack position with its 11-degree running boards. We had unanimous agreement that the best benefit to the new tunnel was akin to Megan Fox changing from a knee-cut skirt into a bikini. Slimmer, lighter, sexier are three adjectives we used.

It’s comfortable in the cockpit, too. Test drivers liked the tall, hooked handlebars and the seat arrangement, but some disliked the handlebar rotation that doesn’t remain on the flat, horizontal plane; rather, the outside bar rotates slightly upward as it travels from centered to lock. Though it can complicate throttle manipulation, the positioning helps the driver lean off the sled into corners easier to improve handling. Getting low and forward helps the Nytro’s front end remain stable.

The Achilles heel of the FX Nytro RTX remains its unpredictable handling that diminishes rider confidence and urges a slower-than-normal pace despite the smooth, throttle-soliciting engine.

In straight-line bumps, the Nytro RTX behaves admirably without the unwanted darting. Driving the Nytro aggressively in choppy corners with common stutter bumps, however, is busy and unnerving. When we hit the stutter bumps we felt too much front end compression. The test sled didn’t include a pump to check the setting on the Fox FLOAT front shocks, but the Cat F6 carried one, and we found the Yamaha’s air shocks at 80 psi. We used the pump to bleed each ski shock 7 psi and resumed testing with better results.

We’ve played with aftermarket skis in the past and improved the Nytro’s handling but the best result comes from having more track on the ground, evident by the 144-inch Nytro XTX crossover sled – Yamaha’s best-handling sled on rough trails.

We don’t have complaints from the performance of the Dual Shock Pro rear skid, and the 2010 calibrations to increase comfort over the smaller stutters was apparent – it’s better than ever. Big suspension hits meet performance demands for this class, too, so nothing seemed compromised with the softer tuning at the beginning of the shock stroke.

So where does that leave the Yamaha? Class competitive but not class leading. We love the aggressive colors for this year and dig the cosmetic upgrade with the tunnel. In a class that emphasizes handling, the Nytro is outclassed, but if Yamaha gets the 121-inch Nytro RTX handling sorted out, this class will be threatened.


Arctic Cat F6 Sno Pro – The Returning Mr. Nice Guy

Now in its fourth season on the snow, the Twin Spar chassis-housed F6 Sno Pro returns to the ring. There are a few subtle changes that net better-than-ever handling from this chassis. The chief handling upgrade are new skis that are a half-inch wider, almost two pounds lighter and they have a stiffer, deeper keel for more positive cornering.

We’ve liked the easy steering effort of the Twin Spar sleds in the past but felt too disconnected from the terrain and found the steering slow to engage. There is more feedback with the new ski design to better detect grip, and it was unanimous that corner push is reduced – and we tested it in tough, soft-snow conditions. The light and linear steering effort remained intact, and the machine cornered flat.

Cat revised the rear of the sled for the upcoming calendar change. Gone is the bulky trunk and rear plastics. It saves 8 pounds, and though a new zippered pouch is sewn into the rear of the seat, the rear looks unfinished. Arctic Cat has accessories to fill the new void.

The stiff Twin Spar chassis has a plush wrapper with its ergonomics and suspension technology. Arctic Cat monikers its F6 Sno Pro with “Body Saving Technology” that only reinforces the chassis goal of comfort and refinement, and it’s perceptible when riding the machine, too. The comfort in the cockpit is noticed the moment a driver settles into the seat behind a functional windshield. Our test drivers thought it was soft and comfortable, but too wide for quick, agile movement, though the slippery seat skin helped navigate around an equally wide console.


The seat is inviting, which is acceptable because the F6 Sno Pro has the least accommodations for stand-up riding. Though the sled is comfortable and steers fine, the seat’s squishy girth meant it didn’t react as quickly as the lighter, slighter sleds in this comparison. It notched the F6 down the favorite ladder when weighed against the most important attributes of the performance middleweights. Because the driver is more isolated from feeling and reading the terrain, the F6 has a less-sporty feel.

The rear suspension handled the terrain variety exceptionally. We noticed great low-speed stutter bump compliance with a wide comfort ratio that isolated all of our riders regardless of size and weight. We also noted fabulous progression with the larger holes.

We’re not issuing a newsflash about the Twin Spar weight. The engine has more work to do, which saps response and rush from the Suzuki 599 twin. That engine has been around the block, and we’ve been expecting a new, more powerful middleweight engine based on the current race engine. In the Twin Spar, the existing plant doesn’t have the mid-range punch the other two-stroke twins deliver. When ridden on its own the machine is OK with its powerband, but it simply doesn’t compare with the off-the-line or top-end pull of the other engines in this fight.

The Arctic Cat F6 Sno Pro is a great snowmobile. The ride quality in the stutter bumps was superior to everything else here. It steers light, it’s all-weekend comfortable, it’s stable and a terrific handler. It’s a capable trail sled and ditch banger. But the comparatively anemic engine knocks it down, and the floating, isolated feel from the terrain reward with industry-leading comfort – and that might be your primary purchase driver. But the middleweight game is about the combination of power, light weight and quick handling. The sum of the parts is uninspiring by comparison.


Polaris Rush – Bringing Intrigue to the Middleweight Arena

The Polaris Rush is not a “me too” snowmobile.
Polaris built its new middleweight hero sled tagged with Terrain Dominating Control marketing. At first glance, this all-new machine stands out like a vegan at a Texas barbecue. Polaris calls its unique rear suspension the industry’s first progressive suspension. We’ll argue against the claim (the first Arctic Cat AWS machines with twin outboard shocks are an example of a progressive, rising shock rate), but the Rush employs sexier packaging, more complex geometry and longer travel. A glance at its tail section is instantly intriguing. Good luck finding anyone who doesn’t want to take one for a spin.

In the crusade against aluminum welding that weaken chassis junctions, Polaris is using a bonding adhesive for many of its chassis members. Engineers claim 50 percent fewer parts and 86 percent fewer welds with the new chassis. The backbone to the Rush is the X-member in the Pro Ride system. The triangulated frame geometry increases structural integrity and reduces chassis flex. Compared to the well handling though flexible IQ chassis, riding the Rush is clearly a tighter sled.

The front suspension has its own components but similar geometry as the prized IQ front end. It handles flat and holds grip in a corner without push except under hard acceleration during corner exits, but it begs riders to be active. Ski-Doo’s REV and REV-XP chassis sleds beg for the driver to stay busy, serving as an integral part of the machine’s overall and best performance. The same goes here, and it’s riotous fun.

Standing was easy for our shorter test drivers, the two tallest testers would opt for a taller riser. The narrow seat and tank design offers plenty of knee room for leaning and riding seated and forward – the right moves to make the front end behave well. The 11-gallon fuel tank made it a bit tall between the rider’s legs, which some drivers felt limited leaning ability. One finger controls the best brake Polaris has ever had.


The Rush Pro Ride rear suspension, the subject matter during sled talk du jour, has unique characteristics. It transfers more weight and has more rider influence than any suspension that comes to mind. Rider position on the seat affects how the machine reacts more than other snowmobiles because of the weight transfer characteristics of the progressive, rising rate rear suspension.

The Rush mastered big bumps but wasn’t as compliant as most other short track sled in stutter bumps at Rode Reports. Stutter bump performance was the weakest point of the sled. We hope that final calibrations bring it around – we know its potential from earlier prototype rides that behaved remarkably well in all terrain. Preload settings on the rear shock affect handling, weight transfer and bump absorption immensely. The compression adjustment also affects ride quality to higher-than-normal degrees, too.

Powering the Rush is the 600 Cleanfire. It’s fun, powerful and responsive and has the typical Polaris mid-range pull. It packs more punch and power than the Cat and it should, based on power-to-weight ratios. It feels comparable with the E-TEC in peak horsepower, but the Polaris engine didn’t run as pure or get near the gas mileage of the E-TEC or of the much more powerful Yamaha Genesis 130FI in our test.

Despite the compromises, the Rush is a sled like no other. The Polaris Rush lives up to its Terrain Dominating Control tagging, but falls short of taking the crown in our 120 hp class shootout.


Ski-Doo MX Z X-RS 600 H.O. E-TEC – Image Is Everything

If a person is looking for the best performance middleweight sled for 2010, the MX Z X-RS (Racing Special) is your ride. It’s the ultimate 120 hp sled, but be warned, it comes at the expense of comfort and is – in many ways – a poor choice for trail riding. But for some people, image is everything. They will forego practicality in favor of X-Team stickers to broadcast the “I’m faster than you” image.

That image comes from the race track and Ski-Doo’s MX Zx race chassis. Ski-Doo’s X-RS is so similar to the Zx racer that creating it was an easy step. Instead of the race engine it has the clean-burning 600 H.O. E-TEC (the 800R PowerTEK is also available) and it has some consumer-purposed differences, but it’s one of two race-ready machines available for 2010.

The X-RS has the latest race sled reinforcements gleaned from snocross and cross country racing. Wider, stronger running boards have a new extruded edge. The rear suspension is reinforced with four rear idler wheels and tougher suspension rails to accept abusive terrain. The reinforcements add weight over the MX Z X package with the same engine, with claims of 448 and 427 pounds, respectively.


The X-RS gets the race department’s new KYB Pro 40 racing clicker shocks. The shocks feature external high- and low-speed compression adjustability and the front shocks add a rebound adjustment. The latest race shop development has the front tuned to reduce diving in cornering and braking.

Compared to the standard XP chassis, the largest difference is the steering geometry. On the X-RS, the steering post is about 2 inches more forward than the trail-made XP. It puts the rider into a more aggressive, attack position. The result on the ground is much quicker steering and easier stand-up ergonomics. The bars are matched with the racing seat that is 1.25 inches taller for the same purpose, and it’s slimmer for easier cockpit navigation.

Other race-chassis differences are consumer-purposed, such as an electric start option and a multi-function gauge. Despite the trail-friendly provisions, Ski-Doo itself acknowledged the image-selling pitch in its press literature, saying of the X-RS, “For the most hard-core enthusiasts who want the features, technology and look of the MX Zx 600RS snocross racing sled, with a more aggressive calibration than the X.”

And more aggressive it is. “I’m hoping that Ski-Doo didn’t build too many of them,” one of our test drivers said. “It performs great, but it’s a sled for one, maybe two percent of riders out there. And most of them already race.”
Race-shop calibration translates to a harsh ride for just about every trail rider. Like the previous 2007-model X-RS and the 2008 Polaris 600RR, the 2010 Ski-Doo MX Z X-RS is a machine that the harder it’s driven the better it performs.

At all the speeds we tested in our varied terrain, the X-RS was predictable. The outside ski stayed planted entering a corner and with the rider more forward over the skis it allowed the operator to drive through the corner on the gas. It took corners with more speed and held its line better than all of the other sleds in this comparison.

In terms of performance and handling, it’s the best sled overall for the middleweight performance title. But it’s only for those who want an extreme sled and prioritize image above comfort. Some enthusiast riders often think they do, but think differently after the sale – which has led racer specials of the past to last only one year.


Ski-Doo MX Z 600 H.O. E-TEC X – The Returning Champ Repeats

For 2010, there were some updates that improve the X for better-than-ever results. Ski-Doo claims pitman arm changes affect the steering ratio to decrease steering effort by 20 percent. We haven’t complained about aggressive steering with the REV-XP chassis, but we’ll take the upgrade.

The front suspension calibration changes were the greatest benefit. There is less high- speed damping and more low-speed damping coupled with a heavier front spring rate. The result is improved comfort and reduced corner dive, and Ski-Doo claims it’s in better harmony with the rear, too. As with previous XP chassis MX Zs, the front end jumped around in some of the larger stutters, feeling less stable and planted than the Cat, Rush and the X-RS. However it never felt uncontrollable, it doesn’t push and it remains the most confidence-inspiring handler.

The X-package Ski-Doo doesn’t win the suspension comfort category. It has an excellent tradeoff in big bump and stutter compliance overall, but Arctic Cat has the most compliant skid and the Rush has the best bump sucking front end. Perhaps surprising, perhaps not – the Ski-Doo MX Z 600 E-TEC X is our repeat champion. Not always are the latest and greatest machines the new class leaders.

Each of the machines in this test is an incredible snow-riding vehicle, and each of the X competitors seems to have a built-in specialty. But those specialties seem to have created a compromise elsewhere in the performance spectrum.

The Yamaha Nytro RTX has the most powerful engine, finish and capable suspensions. But its handling still needs refinement. The Arctic Cat F6 Sno Pro has the best comfort, but doesn’t ride and handle like a lightweight with its dated engine and heavy chassis. The Polaris Rush is a capable handler, the most fun-to-ride Polaris ever and can tackle the largest bumps superbly, but at the expense of performance in the small chop. The Ski-Doo MX Z X-RS has the handling and image but its radical suspension calibrations are for a small, focused demographic.


The Ski-Doo MX Z X, our returning champion, does everything exceptionally well. It seems that in terms of ride, performance and handling, Ski-Doo masters the game presently, much like the Polaris dominance of the 1990s. The X has a powerful, fuel-sipping, quiet and smooth engine. It has suspension to handle all the terrain with ease and has a wide comfort range that required no adjustments for our crew of drivers. It’s only beaten in the handling category by the X-RS.

It’s easy to boil down the rationale for the X victory: in a class that looks for the fewest compromises, the X is the obvious choice. It comes down to a choice between machines with compromises and one machine that doesn’t.

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