Sri Lanka NVQ L3 Motorcycle Mechanic key terms

Equipment worn to reduce injury risk, such as safety glasses, gloves, hearing protection, steel-toe boots and respirators. In a motorcycle workshop it is selected according to the hazard of each task before work begins.

The process of spotting conditions or actions that could cause harm before starting a job. It leads to controls such as guarding, ventilation, correct lifting or isolating energy sources.

A procedure that isolates energy from a machine or vehicle and attaches a warning tag so it cannot be restarted during repair. It protects the mechanic from unexpected movement, electrical shock or stored pressure.

A document supplied with chemicals listing hazards, safe handling, first aid and disposal information. Mechanics consult it before using solvents, paints, adhesives or coolants.

Separating used oil, solvents, batteries, tyres and contaminated rags into labelled containers so each stream is stored and disposed of correctly. This prevents pollution and mixing of incompatible wastes.

Lifting technique using bent knees, a straight back, a close load and help for heavy items. It reduces strain injuries when handling engines, wheels and frames.

A measuring tool with a main scale and sliding jaw used for outside, inside and depth measurements. The vernier scale gives readings to 0.02 mm or 0.05 mm, making it useful for shafts, bores and disc thickness.

A precision instrument with a calibrated screw that measures small dimensions, commonly to 0.01 mm. It is used for piston diameters, valve stems and crankshaft journals, and must be zero-checked before use.

A dial instrument that measures internal diameter and taper in a cylinder. It is set against a micrometer and used to judge bore wear, ovality and whether reboring or honing is needed.

A set of thin metal blades of known thickness used to check gaps. Typical uses are valve clearance, spark plug gap, piston ring end gap and clutch plate clearance.

A wrench that releases or signals at a set torque so fasteners are tightened to specification. Correct use prevents stretched bolts, distorted covers and loosened critical parts.

The manufacturer's stated tightening force for a fastener, often given as a value plus any sequence or lubrication note. It is found in the service manual and followed exactly for safety-critical joints.

An engine cycle of intake, compression, power and exhaust strokes, each taking two crankshaft revolutions. Valves open and close at set points to fill, seal, ignite and clear the cylinder.

An engine cycle where intake, compression, power and exhaust occur within two piston strokes, using ports and crankcase pressure instead of valves. It gives high power for its size but needs oil mixed with fuel.

The small gap between the cam or rocker and the valve stem that allows for heat expansion. Too little clearance can hold a valve open; too much causes noise and reduced lift.

The correct alignment of camshaft marks with crankshaft marks so valves open at the right moment relative to piston position. Incorrect timing can cause poor running or piston-to-valve contact.

A check of cylinder sealing made by cranking the engine with a gauge fitted in the spark plug hole. Low or uneven readings point to worn rings, leaking valves or a failed head gasket.

Machining the cylinder bore with rotating abrasive stones to restore a fine crosshatch pattern. The pattern helps oil retention and ring seating after reboring or glazing removal.

A device that mixes fuel with air using venturi vacuum and jets before the mixture enters the engine. Its settings for idle, needle height and float level affect starting, economy and emissions.

The proportion of air to fuel delivered to the engine, commonly expressed by mass. A rich mixture has excess fuel and a lean mixture has excess air, each affecting power, heat and emissions.

The fuel height maintained in a carburettor float chamber by the float and needle valve. An incorrect level makes the mixture rich or lean across the whole range.

A tapered needle attached to the carburettor slide that controls fuel flow through the needle jet. Moving its clip changes the mixture mainly at part throttle.

A system where an electronic control unit calculates fuel quantity and opens injectors for a measured time. Sensors for air, throttle, temperature and oxygen feed the calculation.

A sensor that reports how far the throttle is open to the engine control unit. Its signal influences fuelling and ignition timing, so a faulty unit can cause hesitation or poor idle.

The moment the spark occurs relative to piston position, usually stated in degrees before top dead centre. It is set by the ignition system and must suit engine speed and load.

A rating of how quickly a spark plug sheds heat from its tip. A plug too hot for the engine can pre-ignite; one too cold can foul, so the maker's grade must be used.

A flexible petal assembly in the intake tract that opens and closes with pressure changes to control mixture flow into a two-stroke crankcase. Worn petals cause hard starting and poor low-speed running.

A number such as 10W-40 that describes how thick oil is when cold and hot. The owner's manual grade suits the engine's clearances and climate, and the wrong grade affects wear and starting.

A device that circulates oil from the sump or tank to bearings and the cylinder head under pressure. Loss of output quickly causes overheating and seizure.

A replaceable element or screen that traps metal particles and sludge before oil reaches critical parts. It is renewed at set service intervals, and some types are cleaned instead.

A circuit of coolant, pump, radiator, thermostat and hoses that carries heat from the engine to the air. It needs correct coolant mix and a working pressure cap to raise boiling point.

A temperature-operated valve that limits coolant flow to the radiator until the engine warms up. A stuck-open unit slows warm-up, while a stuck-closed one causes overheating.

The ratio of antifreeze to water in a cooling system, chosen for freeze and boil protection and corrosion inhibition. Too little protection allows freezing, scale and corrosion; too much reduces heat transfer.

A condition where the clutch fails to transmit full engine torque, so engine speed rises without matching road speed. Causes include worn plates, weak springs or incorrect release adjustment.

The small movement at the lever or cable before the clutch begins to disengage. Correct free play prevents slipping from a preloaded release and drag from too much play.

The measured up-and-down movement of the drive chain at a specified point. Correct slack allows suspension travel without overloading the gearbox bearing or sprockets.

Wearing of the teeth into a hooked shape, usually with a loose chain. Worn sprockets and a stretched chain are replaced as a set to avoid rapid new-part wear.

The temperature at which brake fluid forms vapour bubbles that make the pedal or lever feel spongy. It falls as the fluid absorbs moisture, so fluid is replaced at the maker's interval.

Removing air from the hydraulic brake circuit by forcing fluid through the system and closing the bleed nipple before air returns. Firm lever feel and consistent stopping confirm success.

The minimum friction material thickness at which a pad must be replaced. Checking it prevents metal-to-metal contact, rotor damage and loss of braking.

The measured thickness of a brake rotor, compared with the manufacturer's minimum. A disc worn below the limit can overheat, warp or crack under braking load.

Correct adjustment of wheel position and angle, including rear wheel alignment in the swingarm. Misalignment causes uneven tyre wear, poor handling and increased chain and bearing load.

The amount of side-to-side or radial wobble measured on a rotating wheel rim. Excess runout from a bent rim or poor spoke tension causes vibration and unstable handling.

Safe handling of lead-acid and lithium batteries, including eye protection, correct charging, venting and preventing short circuits. Sulphuric acid and explosive hydrogen gas make care essential.

The voltage or current the alternator and regulator provide to recharge the battery and run loads. Testing it shows whether a flat battery is due to the battery or the charging circuit.

A measurement of lost volts across a cable, switch or connection while current flows. High drop reveals resistance that causes dim lights, slow cranking or sensor faults.

An instrument that measures voltage, resistance and often current and continuity. It is the basic tool for tracing electrical faults and checking sensor and charging circuits.

The condition of the frame being free of bends or twist that misalign the steering head and swingarm. It is checked after a collision because poor straightness ruins handling and tyre wear.

Setting the preload on the bearings that let the fork turn in the frame. Too loose causes knocking and weave; too tight causes heavy steering and bearing damage.

A controlled ride after repair to confirm braking, steering, drive and electrical systems work correctly before the machine is returned. It follows workshop checks and uses a safe route.

The distance or time between scheduled maintenance tasks such as oil changes and inspections. Following it preserves warranty and prevents wear-related failures.

A stored code set by an electronic control unit when it detects a fault in a monitored circuit. Reading it guides testing but does not replace checking the circuit itself.

Restoring damaged internal or external threads with a tap, die, insert or helicoil. Correct repair keeps the original fastener size and torque capacity in aluminium cases and covers.

Engine oil mixed with petrol at the maker's ratio to lubricate a two-stroke engine that has no separate oil supply. Too little oil causes seizure and too much causes smoke and fouling.

A chain driven by the crankshaft that turns the camshaft at half speed in a four-stroke engine. It must be correctly timed and kept tensioned to avoid valve timing errors.