Motor Bike Parts Useful Information Pt3


The transmission on this 1921 ABC motorcycle is located behind the engine and shifts by a long hand-operated lever on its right side.

Most modern motorcycles have a sequential manual transmission shifted by a foot lever. Some motorcycles, and many scooters, use a continuously variable transmission. Other types of automatic transmission and semi-automatic transmission are also in use.

Engine power can be engaged or interrupted through the clutch, 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 input shaft.

Final drive

A shaft final drive is housed within a rear swingarm of a BMW R1200GS

Power transfer from the gearbox to the rear wheel is accomplished by different methods.

Chain drive uses sprockets and a roller chain, which requires both lubrication and adjustment for elongation (stretch) that occurs through wear. The lubricant is subject to being thrown off the fast-moving chain and results in grime and dirt build up. Chains do deteriorate, and excessive wear on the front and rear sprockets can be dangerous. In a chain drive the power is transmitted into the rear wheel via a cush drive. Conventional roller chain drives suffer the potential for vibration, as the effective radius of action in a chain and sprocket combination constantly changes during revolution (“chordal action”). If a drive sprocket rotates at constant RPM, then the chain (and the driven sprocket) must accelerate and decelerate constantly. Most chain-driven motorcycles are fitted with a rubber bushed rear wheel hub to eliminate this vibration issue.

Chain lubrication

Small budget motorcycles may have a totally enclosed drive chain, but this is rare on larger motorcycles, an exception being the Norton rotary bikes. To prevent rapid wear of the chain and sprockets, it is customary to apply a greasy chain-lube via an aerosol. Many riders also fit aftermarket chain-oilers to feed a regular supply of oil to the chain at the rear sprocket.[6] These chain oilers vary in sophistication, but all add significantly to the life of the chain. The custom of lubing by immersing the chain in a tin of hot grease ceased in the early 1970s, once most chains had rubber “O’-rings. The original Suzuki RE5 of 1975 came with a rear chain oiler, but the 1976 model had a sealed chain, and its oiler was deleted as “unnecessary”.

Honda step-thru with an enclosed chain

belt drive is still subject to stretch but operates very quietly, cleanly, and efficiently. A toothed belt is frequently used. However, they are not as durable when subjected to high horsepower as a chain. You can not alter the length and change final drive ratios as easily as chains. They also can not wrap as closely around as chains. And require larger pulleys compared to chain sprockets to get an effective final drive ratio. Replacing a drive belt typically requires removal of the swingarm, since belts cannot be split the way a chain with a master link can.

shaft drive is usually completely enclosed; the visual cue is a tube extending from the rear of the transmission to a bell housing on the rear wheel. Inside the bell housing a bevel gear on the shaft mates with another on the wheel mount. This arrangement is superior in terms of noise and cleanliness and is virtually maintenance free, with the exception of occasional fluid changes. They are the most durable and usually last the life of the motorcycle. However, the additional gear sets are a source of power loss and added weight. A shaft-equipped motorcycle may also be susceptible to shaft effect.

Virtually all high-performance racing motorcycles use chain drive because they are the most mechanically efficient transmitting power to the rear wheel.


A wire wheel and pneumatic motorcycle tyre on a Ural

The wheel rims are usually steel or aluminium (generally with steel spokes and an aluminium hub) or mag-type cast or machined aluminium. Cast magnesium disks, produced by one-step hot forging from magnesium alloys ZK60 and MA-14, are also used for many motorcycle wheels.

At one time, motorcycles used wire wheels built up from separate components, but, except for dirtbikes, one-piece wheels are more common now. Performance racing motorcycles often use carbon-fibre wheels, but the expense of these wheels is prohibitively high for general usage.


Motorcycles mainly use pneumatic tires. However, in some cases where punctures are common (some enduros), the tires are filled with a tire mousse which is unpunctureable. Both types of tire come in many configurations. The most important characteristic of any tire is the contact patch, the small area that is in contact with the road surface while riding. There are tires designed for dirtbikes, touring, sport and cruiser bikes.

Dirtbike tires have knobbly, deep treads for maximum grip on loose dirt, mud, or gravel; such tires tend to be less stable and noisier on paved surfaces.

Sport or performance tires are designed to provide maximum grip for street use on paved surfaces but tend to wear faster.

Touring tires are usually made of a harder rubber compound for greater durability, these may last longer but tend to provide less outright grip compared to sports tires at optimal operating temperatures. Touring tires typically offer more grip at lower temperatures and can be more suited to riding in cold or winter conditions where a sport tire may never reach its optimal operating temperature.

Cruiser and “sport touring” tires try to find the best compromise between grip and durability. These tend to have stronger sidewalls as they are typically fitted to heavier machines.

Motorsport or racing tires offer the highest of levels of grip. Due of the high temperatures at which these tires typically operate, use outside a racing environment is unsafe, typically these tires do not reach their reach optimum temperature which provides less than optimal grip. In racing situations, tires are normally brought up to temperature in advance based on application and conditions through the use of tire warmers.


Front disk brakes with an ABSsensor ring on a BMW R1200RT

There are generally two independent brakes on a motorcycle, one set on the front wheel and one on the rear. However, some models have “linked brakes” whereby both can be applied at the same time using only one control.

Front brakes are generally much more effective than rear brakes: roughly two thirds of stopping power comes from the front brake—mainly as a result of weight transfer being much more pronounced compared to longer or lower vehicles, because of the motorcycle’s short wheelbase relative to its center of mass height. This can result in brake dive.

Brakes can either be drum or disc based, with disc brakes being more common on large, modern or more expensive motorcycles for their far superior stopping power, particularly in wet conditions. There are many brake-performance-enhancing aftermarket parts available for most motorcycles, including brake pads of varying compounds and steel-braided brake lines.

In 1981, BMW introduced an antilock braking system (ABS) on a motorcycle. Other manufacturers have since also adopted this technology. ABS is normally found on motorcycles of 500 cc or greater engine capacity, although it is available on motor scooters down to 49 cc.


instruments in the cockpit of a Kawasaki W800

Most road motorcycles have an instrument panel, usually consisting of speedometerodometer and tachometer.

Fuel gauges are becoming more common, but traditionally a reserve tank arrangement is used with a petcock (petrol tap) on the side of the motorcycle allowing the rider to switch to a reserve fuel supply when the main fuel supply is exhausted. There is not actually a separate reserve tank: The intake for the petcock has two pipes, one extending higher into the fuel tank than the other. When fuel no longer covers the longer pipe the engine will lose power/splutter and the rider switches the petcock to the “reserve” setting, which accesses the shorter pipe. Riders whose bikes lack a fuel gauge (most machines prior to the past few years) usually learn how far they can go with a full tank of fuel, and then use a trip meter if available to judge when they must refill the tank.

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