CVT Engines in ATVs and 4 Wheelers

4 wheelers and ATV's

CVT ENGINES IN ATVS & 4 WHEELERS

PUBLICATION DATE

Many of humanity’s coolest contraptions use simple physics to perform their tasks. The transmission of your ATV or UTV is no different. One of the most common transmission types in these vehicles is the continuously variable transmission, or CVT. 


When you step on the gas, your CVT balances the rotations per minute (RPMs) of your engine with the RPMs of your input shaft, transmitting the power and acceleration to the wheels. This streamlined system allows your ride to work harder in a variety of conditions while shifting seamlessly. 

   

If you’ve ever wondered what’s going on under the lid of your Polaris’s transmission, this article is for you. Harvey is here to explain the ins, outs, unders, and overs of your ATV and 4-wheeler CTVs.



CVT (Continuously Variable Transmission) Overview

The CVT is made up of three major parts: the primary clutch, drive belt, and secondary clutch. 


The primary “drive” clutch is attached to the engine’s output shaft (PTO shaft), and the secondary “driven” clutch mounts to the rear transmission shaft. The drive belt rides between a pair of weighted sheaves on each clutch.  


As the engine accelerates, the sheaves of the primary clutch narrow and engage the belt. In response, the secondary clutch widens to give way, creating a higher gear ratio. As such, the CVT can be seen as having a highest and lowest “gear,” with an infinite number of smaller ratios between. So instead of the pop-and-catch feeling that comes with changing from a larger to a smaller gear on your bicycle, shifting through to full throttle on a CVT is a smooth transmission.

The Primary Clutch

The drive clutch is where the physics magic of the CTV really comes into play. As we’ve covered, the primary is made up of two sheaves mounted on a self-contained shaft, one stationary and one mobile. The mobile sheave is held open by a powerful spring and clutch cap, which keeps shifting to a calculated rate. 

As the motor shaft spins, so does the clutch and the weighted arms inside it. Centrifugal force acts to push these arms away from the clutch center, forcing the mobile sheave to compress. As it engages the belt between the plates, the vehicle “shifts” out of idle and into gear. 

Belt

A CVT would be nothing without a proper belt. Most are made with extremely durable material, such as vulcanized rubber, fiber cord, kevlar, or a polyblend. Depending on your model, your belt may have cog teeth on one or both sides of its face. While the least mechanically complicated part of the CVT, if your belt gives out, you’re not going anywhere. 

The Secondary Clutch

Just as essential as the primary, the driven clutch is mounted to the transmission input shaft of your ATV or 4-Wheeler. 

In contrast to the drive clutch, the larger diameter secondary sheaves are held closed with a spring, not open. As the engine accelerates and the primary sheaves narrow, the belt pulls down on the secondary sheaves, and they respond with precision calibrated resistance. A cam/helix holds the outer sheave to the assembly, which is responsible for proportional belt squeeze and pressure resistance.  

THE BOTTOM LINE

If your ATV or 4 wheeler cvt has seen better days, the best practice is to replace all three components to preserve optimal balance. Harvey’s ATV has the complicated parts covered for you. Check out our clutch bundles here for a tested and guaranteed pair of primary and secondary CVT clutches, fine tuned and balanced out of the box.

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