When you’re out for a ride, your RZR can feel one of two ways when you hit the gas: you either don’t notice it or it feels sluggish. 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 Polaris primary clutch is the first right at the beginning of your drivetrain. It’s the first thing your engine interacts with before 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.
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 RPM climbs 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 RPM drops back down into the optimal range for your vehicle’s acceleration. And then you start the process again.
A CVT clutch changes its shape so the clutch drive belt doesn’t have to shift. That means it can stay in the optimal RPM range all the way until you hit the mechanical limitations of the clutch.
That’s the main advantage of Polaris’ primary 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 boost performance.
Let’s get into the juicy innards of the Polaris primary 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. It rides higher or lower on the sheaves 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 or 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 delivering power to 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. Finding the right balance between the clutch spring and clutch arms can help you maintain that RPM sweet spot.
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 help a RZR primary clutch run smoothly. The roller material, roller bushings, and arm bushings are all crucially important. Polaris has those details perfected, but where we see room for improvement is the balance between the spring strength and arm weight.
That’s where SuperATV Clutch Kits come in.
When we make a clutch kit for Polaris vehicles, all we do is change the spring and clutch arms out for a different set. Sounds simple, right? It’s not!
Changing out the spring for a different one makes big changes to your clutch’s behavior. If it’s too stiff, your clutch stays open too long, which means your RPM will be over the optimal range before you even start moving. If it’s too soft, your clutch will close quickly, so you might never hit the optimal RPM range at all.
We get close to the RPM sweet spot by trying out different springs and measuring the RPM curve. After we get a good candidate, 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 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 have a lot of control. 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.
Once we dial in a weight combo that keeps the machine in the optimal RPM range for as long as possible, the clutch kit is finished.
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 acceleration—perfect for mud and rocks. We make kits designed to give you a higher top speed for wide open racing. And then 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. And with a huge variety, you can find the clutch kit that’s perfect for you. If you’re clutch is beyond saving, you can check out our RZR Primary Clutch Assemblies.