Defining Lightweight Four-Strokes

More is better, less is best

Published in the November 2013 Issue Steve Janes
Viewed 1668 time(s)
"Big, bad and in your face—that’s the Arctic Cat turbocharged M 9000 Limited 162 4-stroke. It has more than enough giddy up and go power.
"The Nytro MTX is the mountain version of Yamaha’s all 4-stroke lineup and comes in two track lengths—153 and 162 inches.
"You can pump up the power of the Nytro MTX with an aftermarket turbo, shown on the Nytro MTX here. That definitely improves the power-to-weight ratio.
The 2014 Yamaha Nytro MTX (left)and 2014 Arctic Cat M 9000 Limited 162.

Sometimes things just don’t quite add up or make sense. For example, horsepower can make light sleds feel heavy, while making heavy sleds feel light. It’s called an oxymoron—a com­bination of contradictory or incongru­ous words.

Yet that best describes four-stroke mountain sleds … or lightweight four-strokes. Just by the nature of being a four-stroke, the sled is already going to be heavier than your basic two-stroke. But if it’s built for the deep powder in the mountains, the sled maker is going to do all that is possible to make it light.

This past winter the SnoWest Snow­Test crew had a chance to ride and com­pare a couple of the more popular four-stroke mountain sleds—the Yamaha FX Nytro MTX 153 and the Arctic Cat M 9000 Limited 162. (Note that Yamaha also makes the model with a 162-inch track and Cat makes an M 9000 model with a 153-inch track. But for our ride those were the two models available.)

Being able to go back-to-back on the two sleds allows you to feel some of the significant differences in handling and riding characteristics. But to experience the subtle advantages and disadvantages within varying snow conditions would take far more time than we’re allotted during the time we have access to both snowmobiles.


Yamaha Impressions

When we first mounted the Ny­tro 153, it was apparent that Yamaha spent a good deal of time designing something that would be ergonomi­cally friendly to the rider. It had the feel of a Cadillac as we cruised down the trail. We’re talking smooth. The suspension was set to erase any small chatter bumps in the trail, giving the feel of gliding down a highway of snow. The seat is soft—maybe too soft with a flavor of spongy … which gives it an old-style feel of sitting down in the seat instead of on top of the sled.

In the corners when you let off the throttle the “jake brake” effect takes over and does two things: it slows your speed while allowing the weight transfer to put more pressure on the skis for turning control. Yamaha has tried to minimize this effect with its “Engine Braking Reduction System” that allows a small amount of air to pass through the fuel injection system when the throttle is released. But you still feel a portion of the engine drag. It is a little heavy steering and you notice Yamaha’s weight on hardpack snow—a heavier engine just puts a little more weight up front and you feel it as you try to turn.

The weight is really noticeable when you go through trail-beaten moguls. If you hit them fast, the suspension takes over and keeps your snowmobile stable and in control … but you feel like you’re holding a jack hammer and you get that bouncing vibration through your shoulders. This is the feel of some of the weight being transferred back to you. No wonder Yamaha riders tend to have strong upper bodies.

Although you feel the weight on hardpack, once you get in the powder, the sled rides light and handles as well as anything out there.

For those who don’t ride Yamahas, the hardest thing to do is to convince yourself this sled will go where you want it to go. You just have to get it in your mind not to worry about the weight. But we admit it’s hard to erase those lingering thoughts that if you get stuck you are going to have some work ahead of you. But in fresh snow, it really is fun to ride. It rides a lot lighter and handles a lot better in fresh snow … and we’re not talking deep powder, we’re just talking a couple of inches of snow on a packed surface makes a huge difference. And the deeper the snow, the better the ride.

It’s one thing to carve up an open meadow or clear hillside. But when you venture into the trees and your lines have to be exact and corners tight, it’s critical your sled reacts to instant commands.

The first thing we noticed is that where the “jake brake” effect helps you on the trails, it hinders you in the trees. In the trees you want the “free wheeling” feel where the sled rolls when you back off the throttle. Even a subtle weight transfer when not expecting it can cause the rider to lose balance and miss a line.

With any four-stroke it’s important to try to keep a constant throttle. Un­like a two-stroke where you can feather it to keep the rpms constant, a four-stroke requires you to hold the throttle to keep the rpms constant. But in the trees, when you let off the throttle to control your speed or make a turn, the sled tends to drag down the forward momentum. If you are standing (like most riders in the trees) this can cause you to tip forward each time you release your throttle. This will put a lot of pressure on your grip and wrists to keep you from falling forward. If you are not used to it, it’s annoying.

There’s also a problem with a nice spongy seat. Although it’s cushy down the trail, in the trees where you have to dance from side to side, the seat gets in your way and hinders your movement.

Although the Nytro doesn’t have great acceleration, the track seems to keep your thrust solid where you feel a solid hook-up to the snow. The sled does get on top of the snow well. You just have to ride it like a 4-wheeler where you maintain a constant and controllable forward momentum to keep moving. You can’t just feather your throttle like a two-stroke.

The ski width (40.8-inch center to center) does cause some concern in the trees and reduces a few of your options when picking lines in tight situations … but you need the width to feel secure on the trail.


ArcticCat Impressions

The Arctic Cat M 9000 has a uniquely different ride from the Ya­maha Nytro.

It feels a little lighter and handles a lot better in the trees. The track tends to work well there. There’s no “jake brake” feeling when you let off the throttle. There tends to be more natural “roll” through the driveline so it doesn’t cause you to tip forward. It has a two-stroke feel, very natural and comfortable.

The chassis has the feel of the moun­tain sleds—you’re upright and in control. The skis also tend to work fine while picking your way through the trees.

On the trail, where the Nytro rides like the Cadillac, the M 9000 has the ride of a muscle sports car. It’s quick, a little stiff and very powerful. You don’t cruise down the trail, you attack it. You dive into corners, and then explode down the straight-aways. If you’re not riding aggressively, you feel like you’re driving a truck. The M 9000 is de­signed for the guy who wants to be on top of his sled and on the edge. It’s not for resting; it’s for racing.

Keep in mind, the M 9000 is tur­bocharged. And when the turbo kicks in, you better have a grip on things … ‘cause there ain’t no lag. It’s hard, it’s sudden and it’s making distance. You better be prepared to keep it pointed where you want to go.

Because of the power, anytime you travel at slower speeds you notice the weight. The trees are a case in point. As you pick your way around in the timber you have to keep moving to maintain some sort of momentum. Stopping in the wrong spot can turn into a lot of work. It’s nice the M 9000 free-wheels so you can constantly keep crawling without constantly getting back into the throttle. As long as you’re moving, it’s surprising what power can do for you when you need to explode out of a hole. But if you’re stopped, explosions tend to go down, not out, leaving you in a big hole with a lot of work ahead.

In open terrain, where you can unleash the power of a turbo, the M 9000 reigns king. It will climb, it will carve, it will sidehill. Bottom line: it will perform.

Cat engineers realized a four-stroke would be heavy. But they did their best to keep the weight to a minimum while stretching its performance to the maximum. If you are all into power and performance, the M 9000 won’t disappoint.


Final Thoughts

One big difference between the M 9000 and the Nytro is in the handle­bars. Although the Nytro bars are comfortable, the M 9000 bars repre­sent a strong pivotal point atop a solid platform where you can control your snowmobile at all times, whether stand­ing or sitting.

Down the trails you also sense two different styles of performance, one being the ride of a luxury vehicle, the other being the ride of a performance vehicle. The Nytro allows the rider to sit back, relax and enjoy the ride. The M 9000 encourages the rider to get his butt off the seat and “ride it like you stole it.”

Both sleds are designed around the latest technology in the industry. Yamaha leans on its reputation of quality finish and dependability. Cat leans on a reputa­tion of performance and results on the race track. We find that it comes down to rider style when it comes to picking a preference between these two sleds.


Yamaha Noteworthy Features

With an over-achieving Genesis four-stroke engine that operates at a torquey, quick-revving mid-130 horse­power range, you really have state-of-the-art technology on your side.

The Genesis high performance en­gine uses Yamaha’s advanced fuel injec­tion system to control fuel flow to the engine, providing spot-on performance and throttle response. A patented rear exit exhaust design maximizes horse­power by using a straight exhaust pipe design. It also reduces the amount of heat produced under the hood while distributing weight to improve the overall balance of the sled.

Also to help with cooling, the Nytro’s airflow design pulls fresh air in from around the headlight and forces it through the radiator fins for high cooling capacity even in low-snow conditions.

We really like how the Maver­ick track works in deep snow. The 15x153x2.25-inch track has a 3-inch pitch and a varied design, allowing more snow to pack in between the lugs for a solid grip on the snow. To assist in flotation, the Nytro MTX comes with saddleless plastic mountain skis. The extra width and deep keel allow for ex­cellent powder handling characteristics.

Yamaha engineers have designed a low center mass with a composite upper skeleton that represents the framework of the chassis. Yamaha has combined geometry and technology in developing a solid front/rear suspension combina­tion. When you combine a shallow approach angle, a semi-coupled design, and lightweight rails, Fox Float 2 and Float XV shocks, you boost the suspen­sion to another level.

Finally, with Yamaha’s electric starter system and digital gauge displays, you have all the comfort features to satisfy even the most discrete riders. More details are available at http://www.ya­mahamotorsports.com/sport/products/modelfeatures/657/0/features.aspx.


ArcticCat Noteworthy Features

The M 9000 features a C-Tec4 turbocharged 1056cc 4-stroke engine (177 horsepower at any elevation and temperature). This is a lot of power coming out of an intercooled turbo system using 9 psi of boost.

And all this power is strapped to Cat’s ProClimb chassis that features an incredibly strong and remarkably light triangulated upper-spar assembly. A two-piece tunnel combines two formed shells with a boxed support structure to create a stable and functional platform. All Sno Pros come standard with a vertical steering post that delivers a more natural handlebar turning arc for a standing rider who wants to counter-steer on steep sidehills.

Cat also takes advantage of its racing technology to create a front and rear suspension system uniquely designed to deal with a variety of terrain found in the mountains. A springless Fox Float 2 air shock in the rear suspension reduces weight while providing a full range of pressure/tuning options. In the front, tall, lightweight ski spindles and widely spaced A-arms provide torsion rigidity and strength while the lower A-arms mount in a 30-degree angle to improve comfort and cornering.

The M 9000 comes with a deluxe digital/analog gauge with altimeter, electric start, push-button reverse, lightweight aluminum bumpers, front-mounted heat exchangers, ice scratchers and the Power Claw track.

More details are available at http://www.arcticcat.com/snow/sled/M9000LTD.

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