What are the differences between a wet motorcycle clutch and a dry motorcycle clutch?

Question

What are the differences between a wet motorcycle clutch and a dry motorcycle clutch?

More specifically, what are the differences in

• applications
• performance
• reliability
• maintenance/repair

Answer 1

I pulled the following information from this site:

Unless you are a professional motorcycle mechanic, you normally can not see whether a motorcycle has a wet or dry clutch just by looking at the bike. But if you know your Italian motorcycles, you probably have a pretty good idea which ones do.

A wet clutch is called wet because it is actually wet with engine oil. The engine oil provides cooling as well as lubrication between the clutch cage and mating parts. Generally, a wet clutch will have a longer life and will take more abuse from the rider. For a beginning rider practicing to get a motorcycle license, a motorcycle that has a wet clutch would be a good choice.

Motorcycle engine oil required for most wet clutch type motorcycles normally is more advanced than standard engine oil. The oil is typically formulated so it will last longer (retain it’s viscosity) and perform better with a wet clutch, since the wet clutch also adds to the heat and shear that oil has to fight against.

A dry clutch does not live in an oil bath, and is simply dry. Since a wet clutch generally lives longer, then why would anyone want a motorcycle that has a dry clutch? One advantage is that a dry clutch does not contaminate the engine oil with the particles that come from normal clutch wear and tear. If you remove the cover from a dry clutch, you will find dust. In a wet clutch design, that dust would essentially get worked into the engine oil and collected by the oil filter.

A dry clutch does not contribute to oil breakdown, so you don’t normally need to buy the fancier, and typically much more expensive, type of motorcycle engine oil. These types of specialized motorcycle oils normally cost roughly 3X the amount of normal oil.

Since it is not spun through the engine oil, another advantage of a dry clutch is that it causes less drag on the engine and therefore robs less power than a wet clutch does.

Italian motorcycles, such as Ducati and Moto Guzzi, have had a long history of having dry clutches. BMW has used dry clutches as well. By listening carefully, sometimes you can actually hear if a motorcycle has a dry clutch because a dry clutch often will rattle a little as long as the clutch lever is held in while the engine is running. This does not necessarily mean that there is anything wrong with the clutch at all, and in fact, this is like music to some motorcycle racing and sport bike enthusiasts.