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Okay, we know you’ve been waiting for this… and so have we! After a 10-year hiatus, it’s high time for Polaris to enter the 4-stroke market.

To say Polaris has entered the 4-stroke market is a gross and almost incalculable understatement. What Polaris has come with is not a “me too” 4-stroke offering but rather a new engine available in multiple MATRYX chassis variants.

Let’s unveil the new ProStar S4 powerplant with a thunderous drum roll. This engine is purpose-built for snowmobile use. Yes, the engine in some ways mirrors the off-road RZR’s 1000 ProStar, however there are material differences not the least of which is a dry sump crankcase to get the engine’s center of gravity as low as possible (the RZR uses a wet sump design).

The new ProStar 4S is a 270/90 degree-firing (Harley-esque) engine replicating the pleasing exhaust cadence of a V-Twin but generated by a parallel twin design.

This design is perfectly suited for snowmobile applications. The parallel twin cylinder profile is a slick fit in the MATRYX bulkhead while the 270/90 firing order produces significantly more torque as well as the aforementioned pleasing exhaust note.

To get air into the new ProStar S4, Polaris has used a double overhead camshaft head design operating 4 valves per cylinder. This is definitely a “Big Gulp” intake capable of producing what Polaris claims as 90-ish horsepower.

The engine employs a highly effective gear driven counterbalance to eliminate vibration. As a result, the engine is as smooth as silk.

Polaris has fitted the new P22 clutch, launched on Patriot Boost last year, to the PTO end of the crank. This clutch uses an idler bearing on the primary post to enhance belt life and make for extremely smooth drive away.


Of great interest to us was the inclusion of a drive-by-wire (DBW) throttle. In the past we have not been big fans of this cable-less design. While we’re not wrong often, we stand corrected after sampling the new S4.

The triple mode electronic throttle flipper is the first such throttle from any OEM that does not demand operation in “Sport” mode. In fact, we operated the 4S in “Standard” mode and found no throttle lag or undesirable hesitation.

This all-new design from Polaris features a brake monitor that will interrupt the throttle if the rider drags his or her finger on the brake lever for more than a couple seconds. This eliminates the potential for brake system overheating – too common on snowmobiles ridden with the operator’s left index finger riding the brake.

Ultimately, you would like to know if the new S4 Pro Star is competitive in the 90-horsepower class – right? Wait no more. Our first impressions led us to believe the new Polaris 1000 cc twin is capable of taking on the current flock of 4-stroke triples.

The S4’s power is torquey, smooth and the seamless packaging of the S4 in the MATRYX chassis means you can order this powerplant in just about every 129 and 137-inch Indy variant.

Take a trip to your local Polaris store and check out the new S4 ProStar!

Visit polaris.com

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