Yamaha focused on reducing rotating weight with its turbocharger – a strategy aimed at lag-reduction and quick spooling to build boost.

The turbo body itself is very light and efficiently cast while ceramic ball bearings are used on the lightweight turbine. Incorporated into the turbo-plumbing is a free-flowing, header-like cast aluminum exhaust manifold – no doubt to handle the voluminous heat generated by a pressurized engine.

This is an incredibly smooth engine. Its 120-degree firing, 3-cylinder design definitely contributes to that smoothness but this engine takes it skyward a whole notch.

Riding a 137-inch Sidewinder SE last winter, we immediately noticed how velvety this engine is at all RPM levels. It’s almost a paradox when you realize the track under you is churning like an Osterizer on nine and snow is being sand-blasted out the snowflap like a snow-Vesuvius.

Meanwhile, this engine is completely manageable and only gets crazy when you, the operator, feed in too much throttle or act stupid with it. Otherwise, it behaves like a neutered Schnauzer.

Here’s where this operating behavior pays off: If you’re riding medium rough trails at a brisk pace, with former turbocharged sleds in this power range we experienced some difficulties with throttle control as your body, in particular, your right thumb responded to the terrain.

The last thing you want is an unpredictable, sudden surge of 180 stallions when you’re off balance or negotiating a series of whoops. The Sidewinder is completely at ease here and it puts the rider at ease, too.

Second, we noticed the balance of the Sidewinder platform as a whole is very good in rough trail situations. Although there is significant weight at play compared to a big-inch 2-stroke, the engineering team has been able to find a sweet spot where the sled doesn’t feel overly heavy between the skis.

Yes, it does feel heavier than a 2-stroke, but not cumbersome or awkward – even when you’re drilling moguls. We suspect much of this is due to precise engine placement and maybe somewhat about balancing the skidframe’s front arm spring pressure to deal with the extra weight up front.

Either way, this sled is a pleasure to ride and it’s one of the reasons Yamaha has made it available in its first year with so many track variants, shock packages and market pigeon holes.

We also noticed the backshifting advantages of a roller secondary clutch on a Yamaha spewing so much power. The new primary is also a good design. It’s a bit larger than the former Yamaha primary and delivers an overdrive situation when the clutches are shifted out.

For sure, this engine will have no problem pulling the overdrive at max speed.

One of our readers, George Thompson, asked us what the future looked like for Arctic Cat’s Snowmobile Division now that the company has been purchased by Textron.

Good question, George, and here are a couple of our thoughts:

1. Yamaha isn’t going anywhere. The agreement between Cat and the Big Y is a good one and it’s proving itself to be profitable over both the short and long haul. Yamaha is saving millions on R&D, tooling and engineering and making millions by selling Yamaha snowmobile engines to Arctic Cat.

2. Arctic Cat wants and needs its relationship to stay in play with Yamaha. Those Yamaha triples are proving to be bulletproof and Yamaha’s influence and knowledge on the quality control side has been a huge boon to Cat’s production quality over the last four years.

3. We already mentioned dealer and retail financing by Textron and it’s a huge factor.

4. Cash: Some of our readers already alluded to it and we see Cat having enough of it to continue their plans for future product development in the snowmobile biz.

5. No, we don’t see Yamaha buying out Arctic Cat. The bottom line is profits – and it’s very profitable for Yamaha to continue forward with the status quo already established between the two companies.

Besides, Cat is sustainably profitable on its own and with some creative management input from Textron, can quickly return to the levels it saw a couple of years ago.

6. Future products: With both companies (Yamaha and Cat) having excellent engineering resources, you just know there’s lots of stuff on the drawing boards waiting to be released over the next couple years.

You bet both companies want to get these new sleds and powerplants on the snow and thus increase customer enthusiasm and boost sales. This duo is better when it’s working together than when it’s separated!

Riding the new Gen-4 in either 129 or 137 track lengths is a new experience.

It neither steers heavily nor produces the twitchy on-center feel of the XP and XS. Despite having the rider more forward, high speed handling is improved.

When pushing the sled in tight trails we found moving the bars more forward and crowding the gas tank was the best place to work from.

The front end stays remarkably flat – a result of the rider’s ability to weight the inside ski by moving far forward and off the side of the seat.

At lake speed it’s more comfortable to move back on the seat. If your Gen-4 has the available bar riser you’ll be able to achieve the posture you want.

We’ve often wondered how far the sport can go with power. Is there an upper limit? This year, the arrival of Arctic Cat and Yamaha turbos seems to indicate there’s room to go higher.

In the case of the Gen-4 850 the ability to have another ten horses on tap compared to the Series III 800 plus a better handling package is highly attractive.

You can carve tight trails faster than on the XS and you can rock a 10-mile lake at speeds the old 800 only dreamed about.

Full pulls past the C-note are handily accomplished with the new 850 but is it faster than the Polaris Liberty 800 HO? The only 800 that can give the 850 a respectable run is the AXYS 800 HO.

Stay tuned as we put our 850 and a Polaris 800 to the test and answer the question everyone is asking.