What Are All the Components of a Motorcycle Engine?

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What Are All the Components of a Motorcycle Engine?

A motorcycle engine is responsible for providing power to a motorcycle for its ability to function. Although other types of motorcycle engines, such as electric motor driven and diesel driven engines, do exist in small quantities, most motorcycle engines in the commercial market worldwide are two-stroke or four-stroke internal combustion engines. Four-stroke engines are the later version and feature transmissions that are engineered into the engine casings. The two components act as a single design. The components of a two-stroke engine are present in a four-stroke engine, but the opposite is not true. General knowledge of the various components of motorcycle engines and their functions and properties is imperative to making an informed purchasing decision.

Motorcycle engines of different types and their various components can be acquired from auto parts stores as well as online from the comfort of one's home. For example, eBay features a large collection of motorcycle engines and individual components in a wide array of associated variants.

Types of Motorcycle Engines

Nearly all commercial motorcycles have petrol internal combustion engines. Strict emission laws have restricted the use of two-stroke motorcycle engines, and as a result of this, four-stroke engines are gaining popularity with the public. Most motorcycle engines are air cooled or liquid cooled. Oil cooling is also utilised in some cases.

Motorcycle engines can be mounted longitudinally or transversely on bikes. For the longitudinal mount, the crankshaft is parallel to the frame. For the transverse mount, the crankshaft is aligned perpendicular to the frame. Motorbikes with longitudinally-mounted motorcycle engines are suitable for shaft final-drive, while the bikes with transversely-mounted engines are suitable for belt or chain final-drive.

Two-Stroke and Four-Stroke Motorcycle Engines

Moving parts in a two-stroke engine are fewer in number, as compared to a four-stroke engine. The latter produces half the number of power strokes as compared to the former. Two-stroke engines are quite powerful for their mass. The acceleration offered by a two-stroke engine is stronger, as compared to a four-stroke motorcycle engine. The top speed, however, is the same for both. Two-stroke engines are typically easier to start. Because of the poorer piston lubrication, however, the life of a two-stroke engine is shorter.

The power delivery in four-stroke engines is gentler, courtesy of a wider power band. The comfort of riding a motorcycle with a two-stroke engine has improved with the addition of technologies like exhaust power-valve systems and reed valves. In four-stroke engines, due to the better combustion of the intake charge, the fuel economy is also better. Because of the various environmental disadvantages, two-stroke motorcycles are being replaced by four-stroke models in developed nations, but they still maintain a large share of the market in developing nations.

Cylinder Heads

The efficiency of combustion and ultimately the power output of an engine is significantly affected by the cylinder head design. The combustion chamber resides within the cylinder for a flat-head cylinder design. It can also be within a depression in the piston crown. Most of the combustion volume, however, is provided by a 'dome' within the cylinder head. Cylinder heads require continuous cooling through either air cooling, liquid cooling, or oil cooling, as they are the hottest part of any motorcycle engine. Cylinder-head types are also used as an identification of engines and bikes by many people. Examples include airhead, oilhead, knucklehead, and panhead.

Valve Control

Valve control is different for different engines. Valves are operated from the 'underhead' cam without any special valve gear in side-valve engines. Pushrods operate the valves in OHV engines. A belt, gear train, chain, or bevel gear drive generally operates the overhead camshafts in OHC and DOHC engines. The number of valve operations per cylinder could be switched among the low, medium, and high speed revolution ranges after Honda equipped the CBR400F with revolution responding type valve pausing mechanisms (REV) in 1983.

Unit Construction

Initially, the engines and gearboxes were separate items, and a primary chain drove the latter. A single unit construction contained both in later designs. The pre-unit models were still being produced by many companies like Enfield and Norton until recently, and Harley-Davidson still makes pre-unit engines. For traditional gearboxes and engines, different lubrication systems had different grades of oil. The same oil, however, is used for modern bikes.

Cylinders and Configuration

Generally, most motorcycle engines can be configured as sixes, fours, triples, parallel twins, and singles. All of these can either be inline or transverse. V-twins and V-fours are examples of V engines, while flat-sixes, flat-fours, and flat-twins are examples of horizontally opposed engines. Wankel engines can be single-rotor as well as twin-rotor. More cylinders are used in bigger motorcycles for increased power and smoothness. Capacity ranges for the various configurations are also variable. Some common configurations are briefly described in the following table:

Configuration

Sub-Category

Brief Description

Single

-

Cylinders are vertical, inclined, or horizontal

Horizontal is most common in step-through motorcycles

Require a heavy-duty gearbox and a larger flywheel than multi-cylinder engines

Small singles are inexpensive to build and maintain

Inexpensive utility motorcycles

Twin

Straight

Most common British motorcycle type until the mid-1970s

Used transversely-mounted with the exhaust pipes at the front and the cylinders side by side above the crankshaft

Generally have only two main bearings

Examples of longitudinal or inline twins include some post-World War II motorcycles

Twin

V-Twin

Cylinders form a 'V' around the crankshaft in V-twin engines

Can be mounted longitudinally as well as transversely in various models

Transverse mounting can create cooling problems

Twin

Flat Twin

Cylinders are horizontally opposed in a flat twin engine (or boxer engine).

Generally mounted with a longitudinal-crankshaft

Cylinders protrude into the airstream in order to air-cool the flat twin

Highly suitable for shaft final drive

Twin

Tandem Twin

Cylinders are longitudinal and two cranks are geared together

Effectively a pair of geared singles

Suitable for two-stroke racers

Triple

Inline Triple

Three-cylinder engines are generally mounted transversely

Triumph specialised in transverse triples

Kawasaki triples were produced in various capacities in the 1970s

Suzuki produced some water-cooled triples

Various race bike triples have been popular with the masses

Four

Inline four

Transversely-mounted inline four engines are the most common four-cylinder motorcycle engines

Straight-fours have dominated the street motorcycle segments (non-cruisers) since the advent of Honda CB750 inline four motorcycle engine

Four

Flat Four

Horizontally-opposed-4 or a flat-4 engine, aka boxer engine, has four cylinders arranged horizontally on the sides of a central crankcase

Two banks of two cylinders are present on either side

Pistons are generally mounted on the crankshaft

Four

V4

The ST series and VFR series of Honda use the V4 engines

Yamaha raced TZ500/700/750s

Almost all motorcycles were fours in the last decade of the two-stroke GP500 era

Examples of V4s include RD500LC

Four

Square Four

A 'U' engine with two cylinders on each side is called a square four

From 1931 to 1959, square four configuration was used on the Ariel Square Four motorcycle

Five

V5

Honda produced some five-cylinder engines for racing, but they are not commercially produced now

Six

Inline 6

From 1978 to 1982, Honda produced 1,047cc Honda CBX

From 1979 to 1989, Kawasaki produced 1,300cc Kawasaki KZ1300

In 2011, BMW produced 1,649cc BMW K1600GT and K1600GTL

Six

Flat 6

Six-cylinder motorcycle engines are currently in production by Honda

Famous flat-6 include Valkyrie, Rune, and Gold Wing

V8

V8

No major motorcycle manufacturer has used eight or more cylinders for engines

The table enlists a general description of the cylinders and configurations. Manufacturers are always experimenting with different ideas for optimised results. A buyer should, therefore, make a purchasing decision based on his or her personal choices after going through product-specific details.

Buying Components of a Motorcycle Engine on eBay

The easiest way of getting down to the right components and the right motorcycle engines in no time is using the search bar on the eBay home page. Enter a query into the search bar to see the relevant results. For some queries, eBay also suggests a few related searches that may help facilitate the purchasing process. You can always shortlist your options by selecting various filters according to your personal preferences.

One smart purchasing technique is to look for the desired item in your locality first. This can be accomplished by entering your postcode. If you are lucky enough to find the desired item in your area, the seller may be willing to allow you to pick it up to avoid the delivery charges. In such a scenario, you can visit the seller and pick up the component at a convenient time as soon as the order is successfully processed. A common and recommended practice is to go through the feedback of a seller before buying in order to have some insight about the seller's business practices.

Conclusion

A motorcycle engine drives a motorcycle by supplying power to the various parts for proper functioning. Internal combustion engines, both two-stroke and four-stroke, are the most popular type of engines used in motorcycles across the world. Other options like electric motor driven or diesel driven motorcycles are found much less often. Recent models feature transmissions that are engineered into the engine casings so that the two components act as a single design. There are many types of inline and transverse motorcycle engines. For increased power and smoothness for bigger bikes, more cylinders are typically chosen by riders.

Basic knowledge of the various components of two-stroke and four-stroke motorcycle engines, including knowledge of cylinders, cylinder heads, valve control, pistons, and crankshafts, is essential for a buyer to make the best decision for his or her needs. eBay features a diverse collection of motorcycle engines and components, or buyers can stick to the traditional method of shopping locally in automotive parts stores.

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