When you're out for a ride on your RZR, or any other UTV for that matter, your machine can feel one of two ways when you hit the gas: it either feels "good," or it feels "bad." That's it. What you don't notice are the hundreds of factors that go into making your machine drive the way it does. Not least of which is your RZR's primary clutch.
The RZR's primary clutch is the first gateway your engine's power has to travel through before it gets to the wheels where that power actually moves you forward. This makes the primary clutch one of the most important parts of your drivetrain, and it's incredibly complex. Making changes to the clutch that seem insignificant can have huge consequences to horsepower, torque, and belt life.
Instead of leaving the ins-and-outs of your primary clutch hidden behind a veil of mystery that can't be understood by the casual rider, let's break it down so you know how this key piece of equipment does what it does.
Polaris' CVT Clutch
The primary clutch on Polaris UTVs is what's known as a CVT clutch. CVT stands for "Continuously Variable Transmission" which basically means it changes gears without changing gears. Hang with me for a minute here.
Most cars shift through different gears as you accelerate. You start in first gear and accelerate easily, but soon your RPMs climb too high and it's harder to accelerate. That's when you shift into second. With each shift, your acceleration stops for a moment and your RPMs drop back down into the optimal range for your vehicle's acceleration and you start the process again. A CVT clutch instead changes its shape so the clutch drive belt doesn't have to shift. That means it can stay in that optimal RPM range all the way until you hit the mechanical limitations of the clutch.
That's the main advantage of Polaris' clutch setup—you get continuous power when you lay on the gas. But the mechanics that go into that process are a little more complicated. If you know what you're doing, you can take advantage of those mechanics to make your machine behave differently and perform better.
Springs, Arms, and Centrifugal Force?
Let's get into juicy innards of the Polaris clutch where you'll find parts that spin, parts that flop, a bunch of aluminum, and a big ol' spring. The primary clutch looks kind of like a couple dinner plates smashed together with some extra hardware on the backside of one. Those dinnerplates are the sheaves—they're what the belt rides on and the belt rides higher or lower depending on how far apart (open) or how pushed together (closed) they are.
When your foot is off the gas, the clutch is fully open because the primary clutch spring holds it open. With the clutch fully open, the drive belt doesn't move and doesn't transfer power to the secondary clutch, transmission, or anywhere else in the drivetrain.
As soon as you touch the gas, the RPMs rise and the clutch starts to close. This makes the two sheaves move closer together and pinch the belt. That pinch is what starts driving the belt and driving the rest of the machine. This is where the magic happens. As the sheaves move closer together, the belt moves further out on the clutch, like a chain on a bike moving to larger gears. Except, because the clutch is CVT, that change is smooth.
The trick is finding the engine RPM that outputs the highest torque and horsepower and making sure the clutch doesn't close too quickly or too slowly so that it maintains that RPM. This is where your clutch arms and clutch springs come in.
The primary clutch spring is trying to keep your clutch open with all its might. The clutch arms fight against the spring by using centrifugal force to try to close the sheaves. Clutch arms at different weights change the rate that these sheaves close. There are lots of little details that make this run smoothly like the material used in the rollers that arms push against, the bushing in those rollers, the bushings in the arms that allows them to pivot, and the machined curve of the top of the arm. Polaris gets those details right so all that matters after that is spring rate and arm weight.
How SuperATV Makes Clutch Kits
When we make a clutch kit for Polaris vehicles, all we do to the primary clutch is change the spring out for a harder or softer spring and change the clutch arms out for a different weight. Sounds simple right? It's not!
Changing out the spring for a different one makes big changes to your clutch's behavior. Too stiff and your clutch stays open too long—your RPMs will be over the optimal range before you even start moving. Too soft and your clutch will close quickly—you might never hit the optimal RPM range at all. We get close by picking a specific spring, but we fine tune it with the clutch arms.
Our clutch arms have three separate weight points along them. This lets us be very precise. After we get the spring we think we need, we slap some weights onto the clutch arms—the same weights we send with our clutch kits for you to use—and give the machine a pull on our in-house dyno. The dyno (short for dynamometer) measures horsepower, torque, and RPM over time.
With data from the dyno, it's easy to see when the machine reaches optimal RPM where HP and Torque are highest, and it's easy to see how long it stays there before over-revving and eventually hitting the rev limiter. The cool part is that because of the three weight locations on our clutch arms, we can change the behavior of the clutch when it first engages, when it fully closes, and everything in between. If it's engaging too late, put an extra half gram nearest to the pivot point. If it over-revs too early, pull some weight off the outmost spot. If the torque dips in the middle, then we can add a little weight to the middle. We have incredibly precise control.
Why Would You Want a New Clutch Kit?
You might be wondering why clutch kits exist at all? Why doesn't Polaris just get the perfect spring and clutch arm balance right from the beginning? The short answer is that Polaris balances their kit for the average rider and doesn't target overall peak performance for some reason. If you've read this far (thanks), you are not the average rider.
We've gotten to know so much about the ins and outs of clutches because that's what it takes to make them better, and to cater them to individual riding styles. We have kits that give you more power right up front for quick torque and power—perfect for mud and rocks. We make kits designed to give you a higher top speed for wide open racing. We also make balanced kits like stock but with more horsepower, more torque, and a higher top speed throughout your clutch's engagement range.
In other words, we make our clutch kits for you.