Almost every major manufacturer offers the belt-driven automatic transmission, though many of the systems differ in engineering and function. Unlike a manual transmission, a belt-driven automatic is designed to provide almost an infinite amount of gear ratios at both high and low speeds, not to mention more convenience. A continuously variable transmission (CVT) relies on many parts to ensure proper function. Here’s a listing of CVT parts, their location and specific duties.
Primary clutch The front clutch or drive clutch is attached to the engine shaft and rotates when the engine is in drive and the throttle is applied. On some models it rotates when the engine is running and on others it moves only when the clutch is engaged. Its movement also drives the driven clutch, which is attached to the transmission shaft.
Secondary clutch The secondary clutch is the rear clutch. The primary clutch engages the driven clutch via the belt. The belt turns the secondary clutch, which is in charge of transferring the drive power to the transmission shaft and ultimately the ground.
Helix Not all automatic ATVs have a helix. If an ATV has one, it’s located inside the driven (or “secondary”) clutch. The helix is a stationary part that has angled ramps. Upshifts or backshifts will rotate a movable sheave and compress or ease pressure on the internal spring, which is compressed between the helix and the movable sheave.
Both a standard angle stock replacement and multi-angle aftermarket helix can be added if the model has a helix.
Belt The belt is the link between the drive and driven clutch and is basically the lifeline inside a CVT. A high-quality belt will withstand more heat in extreme working and riding conditions.
Buttons Buttoms are found inside the drive (flat neoprene button) and driven clutch (tab-style buttons). They are an affordable replacement part within the pulleys, meant to be a wear or maintenance part, but some companies offer more durable replacement buttons that claim to improve shifting.
Roller bushings There are two types of roller bushings. The roller bushings in the drive clutch they are between the buttons. The weights roll on the roller bushings. In a driven clutch, the helix rolls on roller bushings. Roller bushings are generally considered another wear item.
Spider Found in the drive clutch, the spider holds the buttons. A spider usually has three to four flat extensions that vary in shape and size, depending on the model. Its job is to stabilize the moveable sheave in the primary clutch.
Weights Clutch weights are found inside the spider, and they vary by model and are used to set the engine rpm, though they also affect the transmission’s shift rate. Peak rpm and horsepower determine the correct mass of weights needed.
You can choose different weights to fine-tune the upshifts, peak rpm, low-end pull and mid-range hit. Weights look different for specific models. Kawasaki and Polaris use metal flyweights. Yamaha, Suzuki, Arctic Cat and KYMCO models typically use roller weights.
Starter clutch Also known as a sprag clutch, it’s found between the engine and the primary clutch on some machines. At certain rpm, its shoes engage the drum that transfers the power out to the drive clutch.
Springs Machines with a starter clutch have smaller sprag springs. Other CVTs can have two larger clutch springs. The primary spring is found inside the drive clutch. The driven clutch houses the secondary spring. The spring sits inside each clutch and engages as the throttle is applied or released.
