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Motorcycle parts

One page per component: its role in how the bike works, its most common failure modes, the recommended service intervals, and the symptoms to watch for. Tap a tile to open the detailed page and jump straight to the related diagnostics.

Spark plugIgnition
Produces the spark that ignites the air/fuel mixture.
BatteryElectrical
Stores energy for starting and the electronics.
Starter motorElectrical
The electric motor that cranks the engine.
CarburettorFuel system
Meters the air/fuel mixture on non-injected bikes.
Electronic fuel injectionFuel system
Electronically manages fuel metering.
Air filterFuel system
Filters incoming air to protect the engine.
Piston ringsEngine
Seal the piston against the cylinder wall.
Valve stem sealsEngine
Stop oil from running down the valve stems.
Valves & clearanceEngine
Let fresh gases in and burnt gases out.
Timing (chain/tensioner)Engine
Synchronises the valves with the crankshaft.
Head gasketEngine
Seals the cylinder head to the block (compression, coolant, oil).
Drive chainTransmission
Transmits engine power to the rear wheel.
BearingsWheels & bearings
Let the wheels and shafts spin freely.
Two-stroke premixFuel system
The oil mixed with the fuel that lubricates a 2-stroke engine.
Cylinder & pistonEngine
The heart of the engine: the piston slides in the cylinder to compress the mixture and turn the explosion into motion.
Crankshaft & conrod assemblyEngine
Turns the piston's up-and-down motion into rotation — the engine's central axis.
CamshaftEngine
Opens and closes the valves at the right moment (4-stroke engines).
Cylinder headEngine
Closes the top of the cylinder and houses the valves and combustion chamber (4-stroke).
Engine casesEngine
The casing that holds the crankshaft, gearbox and engine oil.
Engine oil & filterLubrication
Lubricates, cools and cleans the engine — and, on a bike, the gearbox and clutch too.
Fuel tank & fuel systemFuel system
Stores the fuel and feeds it to the engine via lines and a tap.
Fuel pumpFuel system
Sends fuel under pressure to the injection system (fuel-injected bikes/scooters).
Fuel tapFuel system
Opens, closes or sets the fuel supply to reserve (carburettor models).
Choke / cold-start enricherFuel system
Enriches the mixture when cold to make starting easier.
Lambda (oxygen) sensorFuel system
Measures exhaust oxygen to fine-tune the mixture (fuel injection).
Ignition coil & CDIIgnition
Generates the high voltage sent to the spark plug at the exact moment of ignition.
Alternator / statorElectrical
Produces the current that recharges the battery and powers the bike while riding.
Regulator / rectifierElectrical
Stabilises and converts the alternator's current to protect the battery.
Wiring harness & fusesElectrical
The network of wires and protections linking every electrical part.
Switches & safety cut-outsElectrical
Kill switch, side-stand, clutch, brake: the safety cut-outs that allow starting.
Cooling systemCooling
Keeps the engine at the right temperature (liquid- or air-cooled).
RadiatorCooling
Heat exchanger that releases the coolant's heat into the air.
Water pumpCooling
Circulates the coolant through the engine and radiator.
Fan & thermostatCooling
Actively cool the engine in traffic and regulate temperature.
ClutchTransmission
Connects or separates the engine from the gearbox to pull away and change gear.
GearboxTransmission
Matches engine torque to speed through different ratios (geared bikes).
Front & rear sprockets (chain kit)Transmission
The sprockets that, with the chain, transmit power to the rear wheel.
Shaft driveTransmission
Transmits power to the wheel via a shaft and bevel gears (some bikes).
VariatorScooter transmission
The heart of a scooter's automatic transmission: a continuously variable ratio.
Drive beltScooter transmission
Links the variator to the clutch: it transmits all the power on a scooter.
Centrifugal clutch & bellScooter transmission
Engages automatically as revs rise to drive the scooter forward.
Variator rollersScooter transmission
Small rollers that, by centrifugal force, make the variator 'shift up'.
Braking systemBraking
Safety component #1: it slows and stops the bike.
Brake padsBraking
The friction pads that press on the disc to brake — a key wear part.
Brake discBraking
The metal track fixed to the wheel that the pads clamp onto.
Brake caliperBraking
The hydraulic 'clamp' that pushes the pads onto the disc.
Master cylinder & brake fluidBraking
Converts lever effort into hydraulic pressure — and the fluid carries it.
Drum brakeBraking
A shoe-type braking system, common on the rear of scooters and small bikes.
TyresWheels & bearings
Your only contact with the road: they transmit acceleration, braking and handling.
Wheels & spokesWheels & bearings
Support the tyre and link the wheel to the hub; part of how the bike handles.
Forks / front suspensionChassis
Absorbs front-wheel impacts and keeps the tyre in contact with the road.
Shock / rear suspensionChassis
Cushions the rear wheel for comfort, grip and stability.
Steering headChassis
The axis that links the forks to the frame and lets you steer.
Frame & swingarmChassis
The structure that ties everything together and gives the bike its rigidity.
Exhaust & silencerExhaust
Expels burnt gases, cuts noise and helps engine efficiency.
Cables, levers & controlsControls
Carry your commands to the engine and brakes (throttle, clutch, brakes, choke).
Gear shifterControls
The foot control that shifts the gearbox up and down.
Catalyseur (pot catalytique)Échappement
Réduit les gaz polluants dans la ligne d'échappement des 4T récents.
Capteur PMH (position vilebrequin)Allumage
Indique au calculateur la position du vilebrequin ; sans lui, ni allumage ni injection.
Motorcycle parts · MotoDiagnostic