A motorcycle transmission is a transmission

Transmission (mechanics)

A machine consists of a power source and a power transmission system, which provides controlled application of the power. Merriam-Webster defines transmission as: an assembly of parts including the speed-changing gears and the propeller shaft by which the power is transmitted from an engine to a...

 created specifically for motorcycle

Motorcycle

A motorcycle is a single-track, two-wheeled motor vehicle. Motorcycles vary considerably depending on the task for which they are designed, such as long distance travel, navigating congested urban traffic, cruising, sport and racing, or off-road conditions.Motorcycles are one of the most...

 applications.

Manual

All manual transmission two-wheelers use a sequential gearbox. Most modern motorcycles (excepting scooters) change gears (of which they will increasingly have five or six) by foot lever. On a motorcycle either first or second gear can be selected from neutral, but higher gears may only be accessed in order - it is not possible to shift from second gear to fourth gear without shifting through third gear. A five-speed of this configuration would be known as "one down, four up" because of the placement of the gears with relation to neutral. Neutral is to be found "half a click" away from first and second gears, so shifting directly between the two gears can be made in a single movement.

Automatic

Automatic transmissions are less common on motorcycles than manual. Types include include continuously variable transmission

Continuously variable transmission

A continuously variable transmission is a transmission that can change steplessly through an infinite number of effective gear ratios between maximum and minimum values. This contrasts with other mechanical transmissions that offer a fixed number of gear ratios...

, semi-automatic transmission

Semi-automatic transmission

A semi-automatic transmission is an automobile transmission that does not change gears automatically, but rather facilitates manual gear changes by dispensing with the need to press...

 and dual clutch transmission

Dual clutch transmission

A dual clutch transmission, commonly abbreviated to DCT , is a differing type of semi-automatic or automated manual automotive transmission. It utilises two separate clutches for odd and even gear sets...

.

Reverse gear

The weight of the largest touring motorcycles (sometimes in excess of 360 kg or 800 lbs) is such that they cannot effectively be pushed backwards by a seated rider, and they are fitted with a reverse gear as standard. In some cases, including the Honda Gold Wing and BMW K1200LT

BMW motorcycles

BMW's motorcycle history began in 1921 when the company commenced manufacturing engines for other companies. Motorcycle manufacturing now operates under the BMW Motorrad brand...

, this is not really a reverse gear, but a feature of the starter motor which when reversed, performs the same function. In earlier times pre WWII, hand-operated gear changes were common, a lever was provided to the side the fuel tank. British and many other motorcycles after WWII used a lever on the right but today gear-changing is standardised on a foot-operated lever to the left.

Scooters

Traditional scooters still have manual gear-changing by a twist grip on the left hand side of the handlebar, with a clutch on a lever also rotating. Increasingly they may be fitted with a continuously variable transmission

Continuously variable transmission

A continuously variable transmission is a transmission that can change steplessly through an infinite number of effective gear ratios between maximum and minimum values. This contrasts with other mechanical transmissions that offer a fixed number of gear ratios...

 or CVT instead, a kind of automatic transmission (as once used in the DAF

DAF

-Science, nature and technology:* Decay accelerating factor, a protein involved in the complement system* Delayed auditory feedback, a device used to delay a person's voice to their own ear, which reduces stuttering and cluttering...

 car) that is stepless. Step-through motorcycles often have a three-speed foot change, but the clutch is automatic.

Clutch

The clutch

Clutch

A clutch is a mechanical device which provides for the transmission of power from one component to another...

 is typically an arrangement of plates stacked in alternating fashion, one geared on the inside to the engine and the next geared on the outside to the transmission

Transmission (mechanics)

A machine consists of a power source and a power transmission system, which provides controlled application of the power. Merriam-Webster defines transmission as: an assembly of parts including the speed-changing gears and the propeller shaft by which the power is transmitted from an engine to a...

 input shaft. Whether wet (rotating in engine oil) or dry, the plates are squeezed together by a spring, causing friction build up between the plates until they rotate as a single unit, driving the transmission directly. A lever on the handlebar exploits mechanical advantage through a cable or hydraulic arrangement to release the clutch spring, allowing the engine to freewheel with respect to the transmission.

Construction

Pre-unit construction

Pre-unit construction

Pre-unit construction, also called separate construction, is a motorcycle engine architecture where the engine and gearbox are separate casings, with their own oil reservoirs, and usually attached to parallel plates that also attach to the frame...

, also called separate construction, is a motorcycle engine architecture where the engine and gearbox are separate casings. In unit construction

Unit construction

Unit construction is a term used to describe the design of larger motorcycles where the engine and gearbox components share a single casing. The term is sometimes applied to the design of automobile engines and was often loosely applied to motorcycles with rather different internal layouts such as...

the engine and gearbox share a single housing.