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Motorcycle Glossary of Terms


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Cafe racer - A style of bike made popular in London in the 1950's when bikes travelled from cafe to cafe.

Cam - Device for opening and closing a valve.

Cam chain - The chain which takes drive from the crankshaft to the camshaft(s).

Camshaft - The mounting shaft for the cam, can be in low, high or overhead position.

Carbon - A very lightweight and rigid material used in aftermarked parts to reduce weight, often used in racing. Improves power to weight ratio and overall look of bike.

Catalytic converter - A device in the exhaust system of some machines which converts certain pollutants in the exhaust gases into less harmful substances.

Carburettor - Used to produce the air-fuel mixture.

cc - Cubic Centimeter.

CDI - (Capacitor Discharge Ignition) a computer controlled Ignition, unit often reprogramable.

CE armour - A system of European grading in motorcycle armour to reduce the chances of being hurt in a motorcycle accident. Compresses on impact.

Chain drive - Primary form of drive from engine to gearbox and secondary gearbox to rear wheel.

Charging system - Description of the components which charge the battery, ie the alternator, rectifier and regulator.

Chicane - A series of track back-to-back left and right hand bends (or vise versa).

Chopper - A motorcycle where the non-essential parts have been removed. Ofter applies to a custom-built motorcycle that may have a rigid frame, extended forks a stretched appearance and often no suspension.

CI - Cubic inch, mainly used in America.

Circlip - A ring-shaped clip used to prevent endwise movement of cylindrical parts and shafts. An internal circlip is installed in a groove in a housing; an external circlip fits into a groove on the outside of a cylindrical piece such as a shaft. Also know as a snap-ring.

Clearance - The amount of space between a piston and a cylinder, between a bearing and a journal, etc.

Clip-ons - Handlebars clamped around the top of the fork tubes, lowering a rider's position for maximum aerodynamics.

Close Ratio - normally found on Racing gearbox.

Clutch - Mechanism that disengages the engine from the wheels.

Coil spring - A spiral of elastic steel found in various sizes throughout a vehicle, for example as a springing medium in the suspension and in the valve train.

Combustion chamber - Area where the fuel/air mixture is compressed and fired, between piston and cylinder head.

Compression - Reduction in volume, and increase in pressure and temperature, of a gas, caused by squeezing it into a smaller space.

Compression damping - Controls the speed the suspension compresses when hitting a bump.

Compression ratio - The fuel/air mixture compression degree.

Countersteering - The input a rider gives to the handlebars in order to steer.

Cp - Candlepower. Bulb rating commonly found on US motorcycles.

Crankcase - The casing enclosing the crankshaft and its attachments.

Crankshaft - The shaft for converting the up-and down piston motion into rotary.

Crossply tyre - Tyre plies arranged in a criss-cross pattern. Usually four or six plies used, hence 4PR or 6PR in tyre size codes.

Cruiser - Generally refers to a motorcycle equipped with a low seat and pullback handlebars, stemmed from the 1960's.

Cylinder - Containing the piston and capped by the cylinder head, is the site of the expansion which provides power.

Cylinder head - In a vertical engine caps off the top end of the cylinder. In a 4-stroke engine carries the valve.