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Mountain 4-Strokes Get a Boost from Turbo

Superior torque and track speed help heavier, more reliable sleds climb the hills
RELATED TOPICS: MOUNTAIN SNOWMOBILE | ARCTIC CAT | YAMAHA | TURBO
2016 Yamah SR Viper M-TX 162 LE MPI turbo 4-stroke snowmobile
Don’t discount the boosted 4-strokes because of weight. But beware: You can’t have baby T. rex arms if you’re going to hold on to this kind of power!
Ryan Thompson - RLT Photos
If there is one thing I have learned while riding mountain backcountry, it’s that having a 4- stroke up there is kinda like changing a tire on the highway. People rubberneck and seem to think out loud, “That poor sucker!”

I own a 2016 Yamaha SR Viper M-TX 162 LE with 3-inch lugs and MPI turbo, and I’ve been on the receiving end of that look. Growing up, I too offered condolences to 4-stroke riders. BUT, the intro of the stock turbo changed everything. 
2016 Yamah SR Viper M-TX 162 LE MPI turbo 4-stroke snowmobile
Big dudes will feel at home on boosted 4-strokes, like slipping into a warm jacket that is finally their size.
Ryan Thompson - RLT Photos
The stock turbo in the mountain sleds of Yamaha and Arctic Cat is finally the special sauce that smooths the playing field between 2- and 4-strokes. The new 4-strokes can go places the 2-strokes can’t, honestly! They break trail in deep powder, and make your 2-stroke friends jealous when you hit wide-open meadows. Let’s just say if you are feeling sorry for someone on a new boosted 4-stroke, then you evidently haven’t taken the time to ride one.

Our turbo time is now!

We spent a few days on the new Yamaha Sidewinder M-TX 162 with the new 998 turbo, and I have talked to a lot of people who had the chance to ride it as well. I have yet to hear many negative remarks. There are always naysayers, but with Arctic Cat unveiling its new 4-stroke King Cat with the same motor at Hay Days, there are two stock powerhouses with more than 200 ponies! Cat seemingly had to release the King Cat given their supply partner relationship as the Cat faithful certainly were not going to let that fly without having the option themselves. Now both these zero throttle lag stallions will be throwing down the high marks in the mountains this winter.

Power-to-weight ratios aside, having the heaviest sled presents some inconveniences, but those weaknesses are dropping off like flies. Riders who take the time to ride the new 4-strokes are rewarded with enough torque to make even the most staunch 4-stroke antagonist smile.

Is weight really an issue?
This past January, a large group of us went for a ride on a bluebird day with about 15 inches of new blower snow. It was an epic day of sledding! Of course, we got off the trail as soon as possible and worked our way through varying terrain. About three hours into the ride, I started to feel the 4-stroke burn in my arms and wrists, and my thumb started to cramp up. “Push through it,” I said.

After making it to our destination and playing around in the pow for a while, it was time to start heading back. Our first obstacle was a fairly steep long pull through the pines. As everyone fanned out, taking his or her line, I started the climb. Halfway up, my forearms and hands started to cramp so badly that I couldn’t turn the handlebars. The story ends with me buried in a tree well, breathing too heavily to be prideful, and in need of the unstuck cavalry.
2017 Arctic Cat M 9000 King Cat turbo 4-stroke snowmobile
Earlier this year at Hay Days, Arctic Cat unveiled a special edition M 9000 King Cat, and it has riders looking forward to 200-plus ponies!
Ryan Thompson - RLT Photos
So the answer, does weight really make that big of a difference? Yes. There are 123.3 lbs. of wet weight separating last year’s lightest and heaviest mountain sleds in the industry (Polaris 800 AXYS Pro-RMK and Yamaha SR Viper M-TX LE with MPI turbo, respectively). I happen to own both and spent a lot of time evaluating the differences. There is a lot of physical exertion needed to throw a 500+-pound sled around, especially when your day is filled with climbing chutes, and boondocking through steeps and trees.

However, it wasn’t just the weight that left me sucking wind and cramping… at least not completely. The real reason I found myself at the base of a tree well is because I’m a sissy. Not just your run-of-the-mill type of sissy … a torque sissy, to be precise. You see, it takes strength to hold onto a more powerful sled. It takes muscle to hang on to a throttle that never quits. But should I blame the manufacturers for building a machine that has that much power?

“Dear Yamaha and Arctic Cat: Your sled goes too fast; it has too much power. My baby T. rex arms just can’t hold on.”  

No, I can only blame myself. Some strength exercises through the warmer months will prove this year that I am no longer the torque sissy who had the group waiting.

Size matters
When I brought a Yamaha into the family, it was met with mixed remarks and a lot of jokes. By the middle of the season I had the same people asking to ride it – especially the big guys.  

For those who shop in the big-and-tall department, the sheer power of the boosted 4-stroke will provide virtual liposuction. No sled is more equipped to transport additional rider weight like a 4-stroke with a turbo, and the power and ease with which it takes you to the top of the hill will make you feel lighter ... and better looking!

In addition, the bigger riders in our group didn’t have as much fatigue as their sissy friends, since their additional mass made the ride much easier to maneuver. I’ve concluded the big dudes in my riding group feel at home on boosted 4-strokes, like slipping into a warm jacket that is finally their size. I know some smaller 2-strokes left them singing the Tommy Boy line in the past, “Fat guy in a little coat,” but no more!
2017 Yamaha Sidewinder turbo 4-stroke mountain snowmobile
Time will tell what the longevity of the new 4-stroke turbos will be, but in the past, 4-strokes have long outlived their 2-stroke counterparts.
Ryan Thompson - RLT Photos
Into the deep
The backcountry has a varied terrain that offers benefits for both 2-stroke and 4-stroke riders. The stock 998cc turbo on the new Yamaha and Cat 4-strokes, however, will allow these sleds to climb and go places the 2-strokes can’t. Why do you think turbo 4-strokes are used on big hillclimb movies such as “Thunderstruck,” where mountain chutes, and steep and deep powder reign supreme.

A 4-stroke rider will want to steer toward wide-open meadows and powder-filled hillsides, where the fun factor of sheer speed and never-ending torque is hard to resist. However, 2-stroke riders will also find 4-stroke turbo owners useful in large quantities of new powder, asking them to break trail so they can follow in their tracks.   

Such was the case when our group went riding after a 3-foot powder dump. The trail was not groomed, and all of the 2-strokers looked at my boosted Viper to lead the way until the terrain opened up.

Reliability is tough to beat

It’s a fact that most 4-stroke sleds outlive most 2-stroke sleds. I’m not revealing any national security secrets with this statement. We’ve all come to expect that our 2-stroke mountain sleds will probably need new pistons and rings every 1,500-3,000 miles, perhaps even less if your 2-stroke has a turbo.

This is fine if you plan to upgrade your machine each year, or if you like to spend every spare moment in the shop making your own repairs. But what about those that just want to purchase a machine and ride it (in other words, gas it and go)?

The 4-stroke is the option for those who don’t want to be tied to the shop. Time will tell what the longevity of the new turbo 4-strokes will be, but it is pretty safe to say your 2-stroke friends will have changed out rings and pistons many times by the time a new 998cc Yamaha motor has issues.

You’ll also experience lower maintenance costs with a 4-stroke. Many of our 2-strokes will burn through 8-10 gallons of oil in a season. With full synthetic starting around $40 a gallon, this can add up. The 4-strokes typically just need an oil change each season, and it can be done yourself with a little know-how.

Yamaha 4-stroke motor reliability cannot be understated. As test rider Kevin Thompson says, “Sleds will always break down in places you shouldn’t be.” Such was the case when test rider Lonnie Thompson lost a piston coming off a big ridge into a canyon. The only way out was up the hill, and they were left using ropes and pure manpower.

Many would contend at least it was a 2-stroke. I can hear the detractors saying, “It would take super human strength to pull out a 4-stroke.” On the other hand, some would argue a 4-stroke would not have broken down in the first place.

No doubt, your 2-stroke budget will need to be more, maybe much more with a turbo. However, if money for parts and spare time for wrenching concern you, then a 4-stroke may be your best option.

That said, we’re anxious to see how long the new Gen4 Ski-Doo 850 2-stroker lasts with its new design inspired by diesel and 4-stroke motors. Will this engine even the reliability scales between 2- and 4-strokes? Time will tell.
Kevin Thompson AmSnow Test Rider
Kevin Thompson
Lonnie Thompson AmSnow Test Rider
Lonnie Thompson
Take 2!
2-strokes are definitely lighter, easier to maneuver quickly in tight situations, and easier to hang on to. They are great for boondocking steep hills through the trees and all-around ditch banging. With a 4-stroke, you get incredible track speed on hills, great top end speed, and the fun factor in wide-open meadows and steep hills is off the charts.

I would have never guessed a 4-stroke could be so much fun until I actually got on one and rode it. I am not going to lie. I used to be a believer of the rumors. But like they say, ignorance is bliss. So before you make a fool of yourself on social media bashing 4-strokes, maybe try one first.
– Kevin Thompson, Test Rider




If you have ever discounted a 4-stroke because of weight, you are really missing out. The weight is most certainly undesirable, but the fun factor is really surprising. The horsepower and acceleration may be similar between the two sleds, but the seat-of-the-pants feel of the turbo 4-stroke is unmatched. The best way to explain it is to compare it to the difference between a diesel truck and a gas motor.

I don’t think most make the connection that a good portion of the fatigue that comes from riding a 4-stroke is due to the fact that you really have to hold on. There is never a moment of rest when on the throttle. When did the riders in this world get to be so lazy?”
– Lonnie Thompson, Test Rider
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