Mailing List
Get the latest news by email.

Your email:

New Members

In order to serve you better, select your area code in the drop down list below.

Aller à la version française

Transmissions and friction clutches in oil bath


by Henri Lebarbé ,

Here's the last chapter in our review of ATV drivetrain components, particularly those found on ATVs with a mechanical transmission that controls shifting and unclutching operations via a foot-actuated lever. While semi-automatic gearboxes also use this system, the difference lies in the direct link between the engine and final drive. Let's have a look at how it all works. I'll even give you a couple of maintenance tips for good measure.

When you hear someone say: ''I have a sport ATV'', you immediately think about a wet-type multiplate transmission and clutch system. Wet? That's right: the clutch mechanism bathes in the transmission oil which lubricates it and cools all the internal mechanical components.

The clutch consists of several components that transfer power and torque from the engine to the transmission's primary shaft. Then, the secondary shaft will continue the torque transfer through a gear assembly and a chain -- it's what's known as the final drive. The main elements include a clutch drum, a clutch basket (or shell), a pressure plate, friction plates (or discs; dry or wet), pressure springs, worms, restraint rings and bearings. It's all connected to a wire-actuated release mechanism (to disengage the clutch) and a lever mounted on the left handlebar.

Two kinds of system are possible for engineers. The first is a classic clutch, controlled by a pushrod that goes through the primary shaft and pushes on the pressure plate located on the outer part of the clutch assembly. If you look at an ATV drivetrain from a rider standpoint, you'll see the plate on the left (or right, depending on the model) just behind the external casing cover of the engine. The clutch mechanism is mounted on the opposite side of the clutch casing cover.

The other clutch system uses a lever mounted directly on the clutch casing. The basket, pressure plate and springs are positioned in reverse order, meaning that the pressure plate is at the bottom of the clutch basket. However, the mechanical effect is the same. The benefits of this configuration are a more direct operation and less components required. This type of clutch is also easier to dismantle when replacing worn discs, for instance.

1 - 2 - 3 >>