BTEB Motorcycle Servicing key terms

Gear worn to reduce injury risk while working, such as safety glasses, gloves, steel-toe boots, hearing protection and a face shield. It supplements, but never replaces, safe work practices and guards.

The process of spotting conditions or actions that could cause harm before work begins, then removing or controlling them. It includes checking spills, sharp edges, hot parts, rotating machinery and electrical leads.

A procedure that isolates energy sources and attaches a warning tag before servicing, preventing unexpected start-up or release of stored energy. Only the person who applied the lock removes it.

Deliberate movement of fresh air through a work area to remove exhaust gas, fuel vapour, paint mist and dust. Good airflow protects lungs and reduces the risk of fire or explosion.

The three elements needed for combustion: fuel, oxygen and heat. Removing any one of them extinguishes a fire, which is why correct extinguisher selection and fuel storage matter.

A document supplied with a chemical that lists its hazards, safe handling, first-aid measures, storage and disposal. Read it before opening solvents, cleaners, brake fluid or battery acid.

A wrench that applies a measured twisting force so fasteners are tightened to a specified value. Correct torque prevents stripped threads, distorted parts and loosened joints.

A set of thin metal blades of known thickness used to measure or set small gaps, such as valve clearance or spark plug gap. Blades should slide with slight drag.

A precision instrument with a calibrated screw that measures outside dimensions to hundredths of a millimetre. It is used for piston, journal and shim thickness checks.

A measuring tool with a sliding jaw and a secondary scale that reads outside, inside and depth dimensions, usually to 0.02 mm. Check zero before each use.

A dial instrument that measures the internal diameter of a cylinder. Readings taken at several heights and directions reveal taper, ovality and wear against the service limit.

An engine cycle completed in four piston strokes: intake, compression, power and exhaust, with two crankshaft revolutions. Valves control gas flow in each stroke.

An engine cycle completed in two piston strokes, with one crankshaft revolution. Ports in the cylinder wall and crankcase pressure changes handle gas exchange, so lubrication comes from oil mixed with fuel.

The ratio of cylinder volume with the piston at bottom dead centre to the volume at top dead centre. Higher ratios raise power and heat, and demand higher-octane fuel.

The small gap between the valve stem and its rocker or cam follower, set with a feeler gauge when the engine is cold or as specified. Wrong clearance causes noise, poor sealing or burnt valves.

The exact points, measured in crankshaft degrees, at which intake and exhaust valves open and close. It must be restored correctly after timing chain or camshaft work.

A rotating shaft with lobes that push valves open at the right moment in the cycle. Its profile and timing determine how much air-fuel mixture enters and leaves.

The machined inner surface of the cylinder in which the piston travels. It is measured for wear, then honed or rebored, and matched to an oversize piston if needed.

The clearance between the two ends of a ring when it sits squarely in the cylinder. Too little gap causes seizure; too much allows blow-by and oil consumption.

Combustion gas that escapes past worn piston rings or cylinder walls into the crankcase. It raises crankcase pressure, contaminates oil and reduces power.

The housing that supports the crankshaft and encloses the lower engine. In four-stroke engines it stores lubricating oil; in two-stroke engines it forms part of the intake path.

A device that mixes fuel with air in the correct proportion for combustion. Jets and slides meter the mixture across throttle positions and must be adjusted for altitude and load.

The proportion by mass of air to fuel delivered to the engine, ideally about 14.7:1 for petrol at stoichiometric conditions. Too lean or too rich affects power, heat and emissions.

Abnormal, explosive burning of the mixture after spark ignition, heard as a sharp knocking. It is caused by excess heat, over-advanced timing, low-octane fuel or a lean mixture.

The moment the spark occurs relative to piston position, usually stated in degrees before top dead centre. Correct timing gives full power; over-advance causes detonation.

The air space between the centre and ground electrodes where the spark jumps. It is set with a feeler gauge to the maker's value and widens as electrodes wear.

A small adjustable screw that sets the fuel or air in the idle circuit so the engine runs smoothly at low speed. It is adjusted after the idle speed is set.

A system in which oil is stored in the crankcase, drawn by a pump, circulated through the engine and returned. The oil level is checked with a dipstick or sight glass.

A measure of how thick or resistant to flow an oil is, expressed in SAE grades such as 10W-40. The first number reflects cold flow and the second hot flow.

Loss of drive caused when the clutch cannot transmit engine torque because plates wear, springs weaken or adjustment is wrong. Engine speed rises without matching road speed.

The small movement at the lever or pedal before the clutch begins to disengage. Correct free play prevents slipping and ensures full engagement.

The up-and-down movement allowed in the drive chain at its mid-point. Too tight damages bearings and seals; too loose risks derailment.

Removing trapped air from the brake circuit by forcing fluid through the system while opening and closing the bleed nipple. Air compresses and makes the lever feel spongy.

Reduction in friction material thickness through use. Pads are replaced before the backing plate contacts the disc, and worn pads also lower fluid level.

The amount the motorcycle settles under its own weight or with the rider aboard, set by preload. Correct sag keeps handling stable and the suspension within its travel.

Free movement in the bearings that locate the steering stem. Excess play causes knocking and instability; too little causes notchy steering and flat spots.

The relationship stating that voltage equals current multiplied by resistance. It guides diagnosis of circuits, such as finding high resistance from an unexpected voltage drop.

An instrument that measures voltage, resistance and often current. Correct range and probe placement are essential to avoid damage or false readings.

A live measurement of voltage lost across a connection or cable while current flows. A high reading shows resistance that starves the component of power.

The amount of energy stored in a battery relative to full capacity, estimated from open-circuit voltage after resting. It falls with age, sulphation and poor charging.

The voltage and current the alternator and regulator supply to the battery and loads while the engine runs. It should sit within the maker's specified range at given engine speeds.

A maker-specified list of checks and replacements at set distances or time intervals. Following it prevents breakdowns and preserves warranty coverage.

The final check of a new or repaired motorcycle before handover, covering fluids, fasteners, tyre pressure, controls, lights and road test. It protects both rider and workshop.

A structured method of tracing a fault back to its underlying origin rather than treating only the symptom. It prevents repeat failures and unnecessary part replacement.

A short, structured conversation that records when and how a fault appears, plus the machine's history. Clear questions narrow diagnosis and build trust.