By Jon Crowley, UTVGuide.net
The job of the transmission is to change the speed ratio between the engine and the wheels. The transmission uses a range of gears — from low to high — to make more effective use of the engine’s torque as driving conditions change. The gears can be engaged manually or automatically. Almost all of today’s UTVs use a type of automatic transmission called a continuously variable transmission or CVT.
Unlike traditional automatic transmissions used in cars that are much too heavy for a side x side vehicle, CVTs don’t have any sort of gears. The CVT operates on a pulley system that allows an infinite variability between highest and lowest gears with no discrete steps or shifts.
- A rubber v-belt
- A variable-input “driving” pulley
- An output “driven” pulley
The variable-diameter pulleys are the key to a CVT. Each pulley is made of two cones facing each other. A belt rides in the groove between the two cones. When the two cones of the pulley are far apart, the belt rides lower in the groove, and the radius of the belt loop going around the pulley gets smaller. When the cones are close together, the belt rides higher in the groove, and the radius of the belt loop going around the pulley gets larger.
One of the two pulleys is connected to the crankshaft of the engine. This pulley is typically called the drive pulley. The second pulley is called the driven or output pulley because the first pulley is turning it. The driven pulley transfers energy to the transfer case and onto the differentials, through the axles and out to the wheels.
That all works great until you modify your UTV. As soon as you change to bigger/more aggressive tires or add more power to your UTV, your clutch works harder and can slip more. Excess heat is a real killer of CVT belts and heat is created by belt slippage. The belt is cooled by air flow, so anything you do to slow the flow of air over your belt will make your belt even more hot.
CVT belts slip as a normal part of operation, but limiting the amount of slip is key. Adding extra weight to the vehicle without changing how the clutch operates will cause more slipping. So will over size tires and added performance (pipe, air filter and other performance work). Added stress on the engine while driving in mud or in the sand dunes will also create belt slip.
A CVT system’s ability to “backshift” is critical to keeping your machine’s engine in its powerband while you’re riding it. A strong backshift is what gives you crisp throttle response when you’re on and off the throttle. As you blast through a turn and hit the throttle, you want your engine to snap right up to the sweet spot in its powerband so it’s pulling hard immediately. Poor backshifting is characterized by a lag in throttle response.
While it is impossible to set up a clutch on a UTV to handle all variations or vehicle weight, horsepower and driving conditions, it is possible to adjust your clutch with different springs and weights for the majority of conditions. Think of it as tuning your CVT to your vehicle modifications and riding areas.
Clutch kits are a package of springs, weights and possibly a new belt that calibrate your clutch to your UTV setup (tires, engine, weight) and terrain (mud, sand, dirt, snow).
Clutch kit features:
- More efficient in transferring the power of your ATV/UTV down to the tires
- Designed to improve low and mid-range acceleration
- Helps to decrease belt slippage, which will decrease clutch heat
- Enhances back shifting and throttle response
Here is an educational video from EPI regarding when you should look at a clutch kit.
EPI has been developing performance Clutch Kits for snowmobiles, ATV’s and UTV’s since 1991. During that time the company has grown from being a basement-based hobby/business to our current Headquarters & Operating Complex in the Baxter, Minnesota industrial park where we ship daily to distributors and dealers around the world.
Over the many years of developing our Clutch Kits, our continued focus and commitment has always been to test every machine right here at our facility, on our own proving grounds where we can apply real-world scenarios and dial in true performance gains that our customers can feel by the “seat of their pants”.
As we grew, it was a natural fit for us to expand into other areas of driveline components such as wheelshafts, CV joints, U joints, bearings, seals and suspension components. We now offer full lines of many driveline components and rebuild kits to restore your machine to like-new functionality.
Our most recent new product launch has been our exclusive line of Severe Duty Drive Belts for ATV/UTV’s. As the industry has grown and enthusiasts found more and more ways to modify and use their machines, we saw the growing need for a “Severe Duty” belt that could withstand the stress and heat of severe applications. EPI’s line of Severe Duty Belts are the best belts you can buy, period.
Although it’s hard work testing all these machines and making sure you have the very best performance products available for your machine, rest assured that we’re dedicated to the task. So don’t worry about us, we’ll just keep on plowing through the mud, climbing the hills, blasting over the dunes and hitting the fresh powder so that you can have the best Clutch Kits and replacement parts available. Really, we’ll be just fine. Now go out and enjoy your ride.
EPI can be found on the web at www.erlandsonperformance.com
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