Motorcycle glossary

ABS stops the wheels locking under hard braking, so the motorcycle stays stable and steerable. How it works and what to check.

A small pump in the carburettor that squirts extra fuel when you open the throttle quickly, preventing a lean stumble.

An adventure bike (ADV) is built for long trips on both tarmac and gravel or dirt, with long-travel suspension and luggage options.

Drag is the air resistance that pushes against a moving bike and rider; it rises sharply with speed and affects top speed and fuel use.

Aftermarket parts are made by companies other than the motorcycle manufacturer (OEM), often as cheaper or upgraded replacements.

An air-cooled engine sheds heat through fins on the cylinder and head into the passing air, with no radiator or coolant.

The air filter stops dust and dirt entering the engine. Paper, foam and cotton types, and how often to clean or replace them.

An air lock is trapped air blocking fluid flow in a brake, cooling, fuel or oil line; vapour lock is fuel boiling in the line.

An air spring uses compressed air instead of a steel coil to hold up the bike. Common in modern motocross forks; set with a pump.

Air-fuel ratio is the mass of air to the mass of fuel entering the engine. Petrol burns completely at about 14.7:1.

In motorcycling, alloy usually means aluminium or magnesium alloy used for wheels, frames and engine parts to save weight.

The alternator generates electricity to charge the battery and run lights and ignition. On most bikes it is a stator inside a magnet flywheel.

An ammeter measures electrical current in amps. Useful for checking charging output and finding a battery drain.

Analogue gauges show speed, revs and other readings with a needle on a dial, rather than on a digital display.

Anodising builds a hard oxide layer on aluminium parts, protecting them from corrosion and allowing bright colours.

Anti-dive forks, common in the 1980s, stiffened the front suspension under braking to reduce nose-dive.

Ape hangers are very tall custom handlebars that put the rider's hands at or above shoulder height, popular on choppers.

The apex is the point where your line comes closest to the inside of a corner. Choosing it well makes cornering safer and faster.

Aquaplaning happens when a layer of water lifts the tyre off the road, so grip, steering and braking are lost.

Arm pump is tight, swollen forearms that lose strength while riding, common in motocross and enduro. Causes and how to prevent it.

The attack position is the ready stance for riding off-road standing up: knees bent, grip with the legs, light hands, eyes up.

A back protector shields the spine in a crash; motorcycle back protectors are certified to EN 1621-2 at Level 1 or Level 2.

A backbone frame uses one large tube or beam from the steering head, with the engine hanging below. Common on small bikes and scooters.

A backfire is a bang from the exhaust or intake when unburnt fuel ignites outside the combustion chamber. Common causes and fixes.

Backing it in means letting the rear wheel slide sideways under braking into a corner, a road racing and supermoto technique.

A bagger is a cruiser or touring bike with hard saddlebags and usually a fairing, built for long-distance comfort.

A balaclava is a thin hood worn under the helmet for warmth, hygiene and comfort, covering head and neck with an opening for the face.

The balance point is where the bike stays upright with almost no correction, whether at walking pace or in a wheelie.

A balance shaft (counterbalancer) is an offset-weighted shaft geared to the crankshaft that cancels part of the engine's vibration.

Ballistic nylon is a thick, tightly woven nylon fabric with good abrasion resistance, used in riding jackets, trousers and bags.

A bash plate protects the engine cases and frame underside from rocks, logs and landings. Aluminium, plastic and composite options.

A motorcycle battery powers the starter and the electrics; the common types are AGM, gel and lithium (LiFePO4).

Electrolyte is the liquid or gel in a battery that lets current flow between the plates; in lead-acid batteries it is diluted sulphuric acid.

Trickle or maintenance charging keeps a stored motorcycle battery full with a small current, preventing winter discharge and damage.

BDC is the lowest point of the piston's travel, where it stops and reverses. Used with TDC for valve and ignition timing.

Bearings let parts rotate or pivot with little friction: wheels, steering head, swingarm and engine. Types and signs of wear.

Belt drive uses a toothed rubber belt instead of a chain to drive the rear wheel: quiet, clean and low-maintenance.

A berm is a banked wall of dirt on the outside of a corner that lets riders turn faster by leaning against it.

A bias-ply tyre has carcass plies running diagonally in a criss-cross pattern. Common on off-road, classic and cruiser bikes.

Big bore means a large-capacity engine, and a big bore kit enlarges the cylinder bore and piston to raise engine capacity and power.

The big end is the end of the connecting rod that runs on the crankshaft pin. A worn big-end bearing causes knocking.

The Big Four are Japan's major motorcycle makers: Honda, Yamaha, Suzuki and Kawasaki.

Bike recovery means getting a dropped, stuck or broken-down motorcycle upright, unstuck or transported safely.

A bikini fairing is a small handlebar or fork-mounted cowl around the headlight that deflects a little wind from the rider's chest.

Billet parts are CNC-machined from a solid block of metal, usually aluminium, rather than cast or forged.

The bivouac is the rally raid camp where riders and teams sleep, service bikes and get the next stage's roadbook.

Black ice is a thin, transparent layer of ice on the road that is almost invisible and extremely slippery.

Bleeding removes trapped air from hydraulic brakes, clutch or cooling systems. Why a spongy lever needs it and how it's done.

A blind corner is a bend where you cannot see the exit because of trees, buildings, a crest or the tightness of the turn.

A blip is a quick stab and release of the throttle, used to match revs when downshifting or to lift the front wheel briefly off-road.

A block pass is an overtaking move where a rider takes the inside line in a corner, cutting across the rival's path to take the position.

Blow-by is combustion gas leaking past the piston rings into the crankcase. A lot of it points to worn rings or cylinder.

Telelever is BMW's front suspension: the fork tubes guide the wheel, while an A-arm and a central shock absorber handle springing and damping.

A bobber is a stripped-down custom bike with shortened ('bobbed') fenders, a solo seat and minimal parts.

Body armour are impact protectors in riding gear for shoulders, elbows, knees, hips and back. CE levels 1 and 2 explained.

A bog is a hesitation or stumble when the throttle is opened, usually caused by a too-rich or too-lean mixture.

Bore is the inside diameter of an engine cylinder. With stroke it sets engine capacity; reboring and oversize pistons restore a worn bore.

The bottom end is the lower part of the engine: crankcase, crankshaft, connecting rod and, on most bikes, the gearbox.

Bottoming out is when the suspension uses all its travel and hits the end stop with a harsh jolt. Causes and setup fixes.

A bow wave is the wave pushed ahead of the front wheel in a water crossing. Ride at a steady speed so it doesn't reach the air intake.

A Bowden cable is a steel inner wire in a flexible outer sleeve, used for throttle, clutch and some brakes. Care and adjustment.

A boxer is a flat engine with horizontally opposed cylinders, famous on BMW twins. Smooth, with a low centre of gravity.

The brake caliper is the fixed part of a disc brake whose pistons press the pads against the spinning disc to slow the wheel.

Brake cylinders convert lever force into hydraulic pressure (master) and pressure into pad or shoe movement (caliper pistons).

The brake disc or rotor turns with the wheel; the caliper squeezes pads against it to slow the bike. Check thickness and runout regularly.

Brake dive is the front fork compressing under braking, so the nose drops and steering geometry gets steeper.

Brake fade is loss of braking power when brakes overheat, from hot pads or boiling fluid. Causes, symptoms and prevention.

Brake fluid transmits lever force to the calipers; DOT 4 and DOT 5.1 absorb moisture, so the fluid is usually changed about every two years.

Brake horsepower is engine power measured at the crankshaft. In Europe power is officially given in kW; 1 kW is about 1.36 PS.

A brake marker is a fixed reference point, such as a distance board, where a rider starts braking for a corner on track.

Brake pads are pressed against the disc by the caliper; the common types are organic, sintered and ceramic pads.

Braking bumps are rows of small ripples before corners on dirt tracks, made by riders braking hard in the same place.

Breakover angle is the steepest crest or obstacle a vehicle can roll over without its underside touching. Key for ATVs and enduro.

A bump start gets a bike with a flat battery running by rolling it in gear and dropping the clutch. Step-by-step and limits.

A burnout is spinning the rear tyre on the spot while holding the front brake, producing smoke. Used in drag racing and for show.

A cafe racer is a stripped-down road bike styled after 1950s–60s British racers, with low bars, a single seat and minimal bodywork.

Measuring calipers (a vernier or digital caliper) measure outside, inside and depth dimensions of parts, typically to 0.02–0.01 mm.

The cam chain links the crankshaft to the camshaft so the valves open in exact step with the piston.

Camber is the inward or outward tilt of a wheel seen from the front, and also the sideways slope of a road surface that drains water.

The camshaft is a rotating shaft with egg-shaped lobes (cams) that open the valves of a four-stroke engine at the right moment.

A can can is a freestyle motocross trick where the rider swings one leg over the seat to the other side mid-air and back before landing.

CAP is a compass heading in degrees used in rally roadbooks; C.090 means ride east. A CAP repeater shows your current heading.

A capacitor, called a condenser in older ignition systems, stores and releases electrical charge to protect contacts or smooth voltage.

Carbon fibre is a light, very strong composite of carbon fibres in resin, used for bodywork, wheels, helmets and protective parts.

A carburettor (carb) mixes air and fuel in the right ratio for the engine, using airflow through a venturi to draw fuel through jets.

Case guards are covers fitted over the engine side covers to protect them from cracks in falls, rocks and debris.

Casing a jump means coming up short and landing on the lip or flat top, so the bike bottoms out hard, often hitting its underside.

A catalytic converter is a part of the exhaust that chemically converts harmful gases into less harmful ones; required on modern road bikes.

CC (cubic centimetres) and CI (cubic inches) measure engine displacement: the total volume swept by all pistons. 1 CI is about 16.4 cc.

CDI (capacitor discharge ignition) charges a capacitor to high voltage and dumps it into the ignition coil to give a strong spark.

CE marking on motorcycle gear shows it is certified to EU protective equipment standards, e.g. EN 17092 clothing or EN 1621 armour.

A centre stand is a fold-down stand under the middle of the bike that lifts the rear wheel off the ground for parking and maintenance.

A chain drive transfers power from the gearbox sprocket to the rear wheel sprocket via a roller chain; the most common final drive on bikes.

Chain lube reduces drive chain and sprocket wear; O-ring and X-ring chains need cleaning and lubing about every 500 km.

Chaps are leather or textile leg covers worn over trousers and fastened at the waist; they give wind protection and some abrasion resistance.

A chase vehicle is a van or truck that follows a group ride, tour or rally to carry luggage, spares and any broken-down bikes.

A motorcycle's chassis is the frame together with the suspension, steering and wheels: everything that carries the engine and rider.

Chatter is a rapid vibration or hop of a wheel, brake or clutch; on bikes it usually means the front or rear tyre hopping in corners or braking.

The black-and-white chequered flag marks the end of a race or session; it is shown to the winner first and then to every rider who finishes.

A chicane is a tight S-shaped sequence of alternating bends on a race track, added to slow riders down before a fast section or corner.

The choke enriches the fuel mixture so a cold carburetted engine starts and runs; switch it off as soon as the engine warms up.

A chopper is a custom motorcycle with a stretched front fork, raked-out steering and stripped bodywork, made famous in 1960s–70s culture.

The Christmas tree is the column of start lights in drag racing: staging lights, amber countdown lights and a green go light.

Chrome plating is a thin, mirror-bright chromium layer applied by electroplating to metal parts such as exhausts, mirrors and trim.

Classic or vintage motorcycles are older bikes valued for their history; the age limit depends on the club, insurer or national historic-vehicle rules.

Clip-ons are separate handlebar halves clamped directly to the fork tubes, giving the low, forward riding position of sports and race bikes.

The clutch connects and disconnects engine power from the gearbox so you can pull away, change gear and stop without stalling.

The friction zone is the part of clutch lever travel where the clutch starts to bite; feathering it gives smooth starts and low-speed control.

The cockpit is the rider's area of the bike: handlebars, controls, instruments and screen as seen from the seat.

The combustion chamber is the space between the piston crown and cylinder head where the air–fuel mixture is compressed and burned.

A commuter is someone who rides to work and back; a commuter bike or scooter is built to be economical, practical and easy in traffic.

Compression is the squeezing of the air–fuel mixture by the rising piston before ignition; low compression means lost power and hard starting.

Compression damping controls how fast a fork or shock compresses over bumps; it is usually adjustable with a clicker on the fork or shock.

Compression ratio is the cylinder volume with the piston at the bottom divided by the volume at the top, e.g. 12:1; higher means more efficiency.

A compression release (decompressor) briefly opens a valve or port to lower compression, making it easier to kick-start or crank a big engine.

The connecting rod links the piston to the crankshaft, turning the piston's up-and-down motion into rotation via its small and big-end bearings.

A constant radius turn is a bend with a steady, unchanging curve, ridden with a fixed lean angle and steady, slightly rising throttle.

The contact patch is the small area of tyre touching the road at any moment, roughly the size of a credit card, which carries all grip.

Coolant carries heat from a liquid-cooled engine to the radiator and protects against freezing and corrosion.

A cooling collar is a neck wrap you soak in water; its gel or crystals hold moisture and cool the neck by evaporation on hot rides.

Cooling fins are the thin metal ribs on an air-cooled engine's cylinder and head that increase surface area so airflow can carry heat away.

Coolmax is a trademarked moisture-wicking polyester fabric used in base layers, socks and liners to keep riders dry and cool.

Cordura is a trademarked range of tough nylon fabrics with high abrasion resistance, widely used in textile motorcycle jackets and trousers.

Corrugations are regular ripples across a gravel or dirt road caused by traffic; they shake the bike hard and loosen bolts over long distances.

Counter-steering means pushing the handlebar on the side you want to turn: push right to lean and go right. It's how bikes turn at speed.

Counterbalancing means leaning the bike into a turn while keeping your body upright over it, weighting the outside footpeg for grip.

The cowboy mount is getting on a tall bike by standing on the left footpeg, then swinging the right leg over the seat, like mounting a horse.

A cowl or cowling is a bodywork panel covering part of the bike, such as a headlight cowl or seat cowl, for looks, protection or aerodynamics.

A CP is a staffed checkpoint in a rally or enduro where officials record that you passed; missing one brings a time penalty.

A cradle frame uses tubes that run down from the steering head and under the engine, holding it like a cradle; single or double cradle.

The crankcase, or engine cases, is the housing around the crankshaft, usually two aluminium halves that also hold the gearbox on most bikes.

The crankshaft turns the pistons' up-and-down motion into rotation, which then drives the clutch, gearbox and final drive to the rear wheel.

Crash bars are steel tubes bolted to the frame on both sides of the engine to protect it, the bodywork and the rider's legs in a tip-over.

Cresting is riding over the top of a hill or dune while controlling speed and body position, since you can't see what lies beyond the crest.

Cross-axle terrain is uneven ground where the wheels sit at different heights or angles, testing balance, traction and suspension travel.

Being cross-rutted means the front and rear wheels are in different ruts, which makes the bike hard to steer and often ends in a fall.

A crossover or balance pipe links the exhaust header pipes of two cylinders, evening out pulses for smoother torque and a different sound.

Crosswinds blow across your direction of travel and can push a motorcycle sideways; gusts are worst on bridges, open fields and past lorries.

Cruise control holds a set speed without the rider holding the throttle; adaptive versions use radar to keep a distance to the vehicle ahead.

A cruiser is a relaxed-style motorcycle with a low seat, forward or mid footpegs, pulled-back bars and usually a V-twin, built for easy riding.

A CVT is the stepless transmission used on scooters and most ATVs: a belt runs between two pulleys whose diameters change with engine speed.

The cylinder is the bore in which the piston moves; the cylinder block or barrel is the casting containing one or more cylinders.

The cylinder head closes the top of the cylinder and forms the combustion chamber; on four-strokes it houses the valves, ports and often the camshafts.

A cylinder liner or sleeve is a replaceable tube inside the cylinder that forms the wear surface for the piston and rings.

A dab is a quick touch of the foot on the ground to keep the bike upright in slow, technical terrain; in trials it costs a penalty point.

Damping controls how fast suspension compresses and rebounds by turning motion into heat in oil; the spring holds the weight, the damper controls it.

Direct current flows in one direction only; a motorcycle's battery and electrical system run on 12 V DC, while the alternator makes AC that is rectified.

Dead centre is where the piston stops and reverses: top dead centre (TDC) at the top of the stroke and bottom dead centre (BDC) at the bottom.

Decarbonising means removing carbon deposits from the piston, combustion chamber, ports and exhaust; especially important on two-strokes.

A decreasing radius corner tightens as you go through it; enter slower and with a later apex so you have room to turn more.

A deflector piston has a raised ridge on its crown that steered fresh mixture upward in early cross-scavenged two-stroke engines.

Denier measures the weight of the yarn in a fabric; higher denier usually means a thicker, more abrasion-resistant textile jacket or trousers.

Desmodromic valves are opened and closed by cams and rockers instead of springs; Ducati made the system famous on road bikes.

Detailing is thorough cleaning, polishing and protecting a motorcycle, from wheels and chain to paint, plastics and metal parts.

Detonation, or knock, is uncontrolled explosive burning of the mixture after the spark; it sounds like pinging and can damage pistons.

A diamond frame has no lower cradle under the engine; the engine itself is a stressed member, giving a diamond-shaped side profile.

Dieseling, or run-on, is when a carburetted engine keeps firing for a moment after the ignition is switched off, usually from heat or carbon.

A rally roadbook displayed on a tablet or dedicated rally screen instead of a paper roll, scrolled with a handlebar remote.

A dipstick is a rod or dipstick plug used to check engine oil level; some bikes use a sight glass instead. Check with the bike upright.

A dirt bike is a light off-road motorcycle with long-travel suspension and knobbly tyres; motocross models are not road legal, enduros can be.

Disc brakes stop the bike by clamping pads onto a disc (rotor) bolted to the wheel; check disc thickness and pads regularly.

Displacement is the total swept volume of an engine's cylinders, given in cc; it sets licence and tax classes but doesn't alone decide power.

A distributor routes high-voltage current to each spark plug in turn; once used on some classic motorcycles, modern bikes have electronic ignition.

DNF means did not finish, DNS did not start and DSQ (DQ) disqualified; you see these in motocross, enduro and road race results.

DOHC engines have two camshafts in the cylinder head, one for intake and one for exhaust valves, allowing high revs and four valves per cylinder.

DOT is the US Department of Transportation; a DOT sticker means a helmet meets US standard FMVSS 218, which is not the European ECE 22.06.

A double jump is two jumps cleared in one flight over the gap; a triple clears three. Typical of motocross and supercross tracks.

The double blip is a trials and enduro technique: one throttle blip lifts the front onto an obstacle, a second drives the rear wheel up and over.

Double track is an unpaved trail wide enough for a car or ATV, with two wheel ruts, as opposed to narrow single track.

A doughnut is spinning the bike around the front wheel with the rear tyre smoking or roosting, leaving a circle of rubber or a ring in the dirt.

Downshifting is changing to a lower gear to slow down or get more pull; match revs (blip) and release the clutch smoothly to avoid rear-wheel hop.

Drag bars are low, flat, straight handlebars, popular on custom and cruiser bikes; they give a forward-leaning, sporty riding position.

Drag pipes are short, straight, usually baffle-free exhaust pipes on custom bikes; they are loud and normally not road legal in Europe.

Dragging pegs means the footpegs touch the road in a corner because of lean angle; a warning that ground clearance is almost used up.

A dragon back is a motocross obstacle of several small jumps in a row, like a spine, that skilled riders skim or jump in one go.

Drifting is deliberately sliding the rear tyre through a corner under power or braking; common in dirt track, supermoto and off-road riding.

A drum brake presses curved shoes outwards against the inside of a drum in the wheel hub. Found on small bikes, scooters and classics.

A dry-sump engine stores its oil in a separate tank, with a pump scavenging oil from the crankcase; common on motocross and enduro four-strokes.

A dual-sport is a road-legal motorcycle built to ride both on tarmac and off-road, from light trail bikes to large adventure bikes.

Duck walking is moving the bike forward while seated by paddling with both feet; useful in deep mud, sand or tight spots, but risky for ankles.

The dune crest is the top ridge of a sand dune; a false crest only looks like the top and hides more climb or a drop behind it.

Reading dunes means judging slope, wind, sand and shape to pick a safe line, including through transitions, dunettes and big ergs.

Dune riding means crossing sand dunes: read ripples and slip faces, ride crests carefully and never drop blind over the top.

Dynamic balance is keeping the motorcycle stable while it moves, using steering, throttle, body position and smooth inputs together.

A dynamo is an engine-driven generator that produces direct current via a commutator; on older bikes it has been replaced by the alternator.

The ECU (or ECM) is the engine computer that controls fuel injection, ignition timing and, on modern bikes, riding modes and traction control.

Edge traps are raised edges of ruts, seams, tram lines or road repairs that can catch a tyre running alongside them and upset the bike.

In drag racing, elapsed time (ET) is how long a bike takes from leaving the start line to crossing the finish line, usually over 1/4 mile or 201 m.

Electronic ignition uses sensors and electronics instead of mechanical points to time the spark; it is reliable and needs almost no maintenance.

The elephant turn is a way to turn an off-road or adventure bike around on a narrow trail by pivoting it in steps, often through 180°.

An endo is when hard front braking lifts the rear wheel; done on purpose it is a stoppie, by accident it can throw the rider over the bars.

Enduro is off-road endurance racing on mixed terrain against the clock, and also the name of the light, often road-legal bikes built for it.

The engine block is the main structure of the engine that holds the cylinders. On bikes it often combines with the crankcase.

Engine braking is the slowing effect when you close the throttle in gear; strongest on big four-strokes and in low gears, weak on two-strokes.

An engine cycle is the sequence of intake, compression, power and exhaust; a four-stroke needs four piston strokes for it, a two-stroke two.

Engine guards, or crash bars, are steel tubes bolted to the frame that protect the engine, tank and bodywork if the bike falls over.

The kill switch on the right handlebar stops the engine by cutting the ignition and fuel pump; use it in an emergency or after a crash.

Motorcycle engine oil must suit a wet clutch (JASO MA/MA2); viscosity such as 10W-40 is chosen from the manufacturer's manual.

Seizure is when moving engine parts lock together due to overheating or lack of oil; a seized piston can lock the rear wheel.

Valves open and close the intake and exhaust ports of a four-stroke engine, letting mixture in and exhaust gases out of the combustion chamber.

An escape route is a way out you pick before entering tricky terrain or traffic, so you can avoid a hazard if things go wrong.

A baffle is the insert inside a silencer that reduces exhaust noise. Removing it makes the bike louder and often not road-legal.

The exhaust system carries burnt gases away from the engine through headers, catalytic converter and silencer, and shapes power and noise.

Fairings are the body panels on a motorcycle that cut wind resistance and protect the rider from wind and weather; usually ABS plastic or composites.

A false neutral is when the gearbox slips between two gears and the engine revs without driving the wheel; usually from a lazy or incomplete shift.

Feathering the brake means applying light, controlled pressure on the brake to manage speed, especially at low speed or off-road.

Fesh fesh is extremely fine, powdery sand or dust with a crust on top; it hides holes and makes bikes sink and lose grip.

The FIM is the world governing body of motorcycle sport, sanctioning MotoGP, MXGP, EnduroGP, trials and more, with national federations as members.

The final drive carries power from the gearbox to the rear wheel; motorcycles use a chain, a toothed belt or a shaft.

Fishtailing is when the rear wheel slides from side to side, usually from too much throttle on a slippery surface or a locked rear brake.

Flat landing is overshooting a jump's landing slope and coming down on flat ground, sending a hard impact through the bike and rider.

A flathead or side-valve engine has its valves in the cylinder block beside the piston, giving a flat cylinder head; famous on old Harley-Davidsons.

Floorboards are large, flat foot platforms used instead of footpegs on cruisers and touring bikes, letting the rider move their feet for comfort.

The flywheel is a heavy rotating mass on the crankshaft that smooths engine pulses; on bikes it often carries the alternator magnets.

Footpegs are the rests for the rider's and passenger's feet; off-road pegs are wide and serrated, road pegs are rubber-covered or knurled.

Fork dive is the front suspension compressing under braking as weight shifts forward; too much dive means soft springs or worn damping.

Fork oil creates the damping in the front forks; its viscosity and level change how the fork behaves.

Fork oil seals and dust seals keep the fork oil in and the dirt out; a leaking seal should be replaced promptly.

Formation riding is riding in a group in fixed positions, usually staggered, so riders keep safe gaps and stay together.

Four-season gear is waterproof, breathable textile riding gear with removable linings, designed for riding from cold spring to hot summer.

A four-stroke engine completes intake, compression, power and exhaust strokes over two crankshaft turns, using valves to control gas flow.

The neck is the front part of the frame where the steering head bearings and the fork's steering stem are housed.

Frame sliders, or crash bungs, are plastic pucks bolted to the frame or engine that touch the ground first in a fall, protecting the fairing.

Freestyle motocross is a judged discipline where riders perform tricks in the air off big ramps; scores reward difficulty, style and variety.

The front fork holds the front wheel and provides front suspension, usually with two telescopic legs containing springs and damping oil.

Tucking or washing out the front means the front tyre loses grip in a corner and the bars turn in sharply, often causing a low-side crash.

Electronic fuel injection sprays pressurised fuel through injectors, metered by the ECU, replacing the carburettor on almost all modern motorcycles.

A fuel injector is an electrically controlled valve that sprays a precise, atomised dose of fuel into the engine.

The fuel pump supplies a fuel-injected engine at a fixed pressure; some carburettor bikes use a vacuum pump.

A full-face helmet covers the whole head with an integral chin bar and visor, offering the most crash and weather protection.

A full-lock turn is a tight low-speed turn with the handlebars at the steering stop, controlled with clutch, throttle, rear brake and balance.

A G-out is a sharp dip or compression where suspension bottoms out as the bike goes from downhill straight into uphill.

A gap is the open space between a jump's take-off and its landing that you must clear in the air.

A gasket is a seal fitted between two mating engine or chassis parts to stop oil, coolant, fuel or gas from leaking.

Gauges are the instruments that show the rider speed, engine rpm, distance, fuel level, temperature and warning lights.

Gear oil lubricates a separate gearbox or final drive on two-strokes, scooters and shaft-drive bikes.

Gear ratio is how many turns the driving gear makes for one turn of the driven gear; it sets acceleration versus top speed.

Gear whine is a high-pitched noise from gears, usually caused by wear, poor meshing or worn bearings.

The gearbox holds sets of gears that let the engine stay in its useful rpm range at any road speed.

GORE-TEX is a waterproof, windproof and breathable membrane used in motorcycle jackets, trousers, boots and gloves.

GPS is a satellite navigation system that lets a receiver work out its position; on a bike it powers sat navs and trackers.

A GPX track is a recorded or planned route saved in GPS Exchange Format for use on navigators and riding apps.

Graphics are the printed vinyl decals applied to a bike's plastics, tank or fairing to style and protect them.

The green flag signals that the race or session has started or that the track is clear after a hazard.

A grey import is a motorcycle brought in privately from another market rather than through the official importer.

The grid is the set of marked starting positions where riders line up before a road race.

Ground, or earth, is the return path of a bike's electrical circuit, usually the battery negative connected to the frame.

Ground clearance is the distance between the ground and the lowest part of the motorcycle, excluding the wheels.

GS is BMW's name for its on/off-road adventure models, from the German 'Gelände/Straße' – off-road/road.

The gudgeon pin, or wrist pin, joins the piston to the connecting rod and lets the rod pivot as the piston moves.

A hairpin is a very tight bend of roughly 180 degrees, common on mountain roads and some race circuits.

Hand signals are gestures motorcyclists use to communicate in group rides, such as warning of hazards or stopping for fuel.

Handgrips are the rubber or foam covers on the handlebar ends that the rider holds; the right one turns the throttle.

Handguards protect hands and levers from branches, roost and crashes. Open roost deflectors vs wraparound guards like Barkbusters.

Handlebar risers raise and sometimes move the bars back, improving riding position seated or standing on the pegs.

Hard armour is impact protection built from rigid plastic shells over foam, spreading the force of a blow over a larger area.

Hardpack is a firm, compacted dry dirt surface that offers less grip than it looks and can be slippery when dusty.

A hardtail is a motorcycle frame with no rear suspension; the rear wheel is fixed rigidly to the frame.

A hare scramble is a US-style off-road race of several laps on a marked woods course lasting a set time.

Harshness is a jarring, uncomfortable feel from the suspension when it fails to absorb sharp bumps smoothly.

The head gasket seals the joint between the cylinder head and cylinder, holding in combustion pressure, coolant and oil.

Head shake is a rapid side-to-side oscillation of the handlebars, usually triggered by bumps or a light front wheel under acceleration.

The header is the first section of the exhaust, the pipes that carry gases from the cylinder head to the silencer or collector.

The visor is the clear shield on the front of a helmet protecting your eyes and face from wind, rain, insects and stones.

A high-side is a crash where the sliding rear tyre suddenly regains grip and throws the rider over the top of the bike.

Highway pegs are extra footrests mounted forward on crash bars so the rider can stretch their legs on long rides.

The holeshot is being first into the first corner after the start of a race, a big advantage in motocross.

Horsepower is a unit of engine power; in Europe power is officially given in kilowatts, with 1 metric hp (PS) = 0.735 kW.

The Hurt Report is a landmark 1981 US study of motorcycle crash causes, led by Professor Harry Hurt.

A hydration pack is a backpack with a water bladder and drinking tube, letting you drink while riding enduro or adventure.

Hydrolock happens when water or fuel fills a cylinder; liquid cannot be compressed, so the piston stops and parts can bend.

A hydrometer measures the specific gravity of battery acid to show the state of charge of a flooded lead-acid battery.

ICO is riders' name for a rally trip meter showing total and partial distance and heading; ICO correction aligns it with the roadbook.

Idle mixture is the air-fuel ratio the engine runs on at tickover, set on carburettors with the pilot air or fuel screw.

The ignition coil is a transformer that steps up 12 V battery voltage to the tens of thousands of volts needed for a spark at the plug.

Retarding the ignition makes the spark happen later, closer to top dead centre; the opposite of advance.

The ignition system creates the high-voltage spark at the spark plug that lights the fuel-air mixture in a petrol engine.

Ignition timing is when the spark fires relative to piston position, usually given in degrees before top dead centre.

An impeller is a rotor with vanes that moves liquid, as in a water pump or the jet drive of a personal watercraft.

An increasing radius turn opens up as you go through it, allowing the rider to add speed and lift the bike towards the exit.

Indicators are flashing lights at the front and rear of a bike that show other road users which way you intend to turn.

An inline four is an engine with four cylinders in a single row, known for smooth running and high revs.

An inline six has six cylinders in a row; on motorcycles it is rare, used by bikes such as the BMW K 1600 and Honda CBX.

An inline triple has three cylinders in a row, combining twin-like low-down torque with four-like top-end power.

An inner tube holds the air inside the tyre on spoked rims and on most motocross, enduro and classic bikes.

The Iron Butt Association certifies long-distance rides such as the SaddleSore 1000: 1,000 miles (about 1,600 km) in 24 hours.

The Isle of Man TT is a road race on closed public roads, first held in 1907; it is among the oldest and most dangerous races in motorcycling.

A jet is a precisely sized brass orifice in a carburettor that meters how much fuel flows into the air stream.

The jet needle is a tapered needle attached to the carburettor slide that meters fuel at part throttle.

A jet ski, or personal watercraft (PWC), is a small sit-down or stand-up craft driven by a water-jet pump instead of a propeller.

A jockey wheel is a small roller or guide that keeps a drive chain or belt tensioned and on track.

The face of a jump is the take-off ramp you ride up; its steepness and shape decide how the bike leaves the ground.

A jump start gets a bike with a flat battery running by connecting it to another battery or a portable booster.

Kangaroo leather is a thin, light and very strong hide used in premium racing suits, gloves and boots.

Kevlar is DuPont's strong, heat-resistant aramid fibre used to add abrasion resistance to riding jeans, jackets and gloves.

A keystone frame is an open diamond-type frame with no down tubes, using the engine as a stressed structural member.

A kicker is a steep, abrupt jump face that throws the bike upwards, or a bump at the base of a jump that kicks the rear wheel up.

A kickstart is a foot lever that turns the engine over through a ratchet mechanism to start it without an electric starter.

The kilowatt is the SI unit of power used in EU documents for engine output; 1 kW equals about 1.36 metric horsepower.

Knee sliders are replaceable plastic pucks on the knees of leathers, letting the rider touch the track while cornering.

A knobby tyre has a tread of raised rubber blocks that dig into dirt, mud and sand for grip off-road.

Lane splitting means riding between lanes of slow or stationary traffic; whether it is legal depends on the country.

A lapper is a rider a full lap behind the leaders; lap traffic is the slower riders the leaders must pass.

Launch control is an electronic aid that limits revs and wheelspin or wheelies for the quickest possible start.

The layshaft is the gearbox shaft parallel to the mainshaft that carries the other half of the gear pairs.

An LCD is a liquid crystal display used in many motorcycle dashboards to show speed, rpm, fuel and other information.

The LCQ is a final short race that gives riders who failed to qualify through heats one last chance to reach the main event.

A Le Mans start has riders run across the track to their parked bikes, start them and ride off, as in endurance racing.

A lean mixture has too much air for the amount of fuel; it makes an engine run hot and can cause damage.

Leathers are leather riding suits, jackets and trousers that give strong abrasion resistance in a crash.

A liaison is the untimed road section that links the bivouac, service and timed specials in rally raids and enduro events.

The line is the path a rider chooses through a corner or terrain; line selection weighs speed, grip, obstacles and safety.

The lip is the top edge of a jump's take-off ramp, where the bike leaves the ground.

A water-cooled engine uses coolant pumped through the engine and a radiator to control temperature, allowing tighter tolerances and steady performance.

Loam is soft, crumbly soil of sand, silt and clay that gives excellent grip for dirt bikes when moist.

Lock-on grips clamp to the handlebar with small bolts instead of glue or wire, so they never twist and are quick to change.

A loopout is when the front of the bike rises uncontrollably in a wheelie and flips over backwards, often throwing the rider off.

Loose over hard is a slippery surface of sand, dust or gravel lying on top of firm ground, typical of gravel roads.

A low-side is a crash in which the tyres lose grip in a turn and the bike slides out on its lower side.

Low-speed control is the skill of manoeuvring a bike precisely at walking pace using balance, clutch, throttle and rear brake.

The lubrication system supplies oil to an engine's moving parts to reduce friction, carry away heat and keep them clean.

Lugging means riding in too high a gear for the speed, so the engine labours at low rpm under load.

A magneto is a self-contained generator that uses permanent magnets to make ignition current without a battery.

The mainshaft is the gearbox shaft that carries the clutch and takes drive from the engine; it is not the same as a driveshaft.

A manifold is the set of pipes that carries air-fuel mixture into the engine (intake) or exhaust gases away from it (exhaust).

A marathon stage is a two-day rally-raid stage where riders get no team help overnight and must service their own bikes.

The master cylinder turns lever or pedal force into hydraulic pressure that operates the brake calipers or a hydraulic clutch.

A master link is a removable chain link used to join a drive chain; it comes as a clip-type or rivet-type link.

Metal fatigue is cracking caused by repeated load cycles, even well below breaking strength; it affects frames, bolts, spokes and brackets.

A metric cruiser is a cruiser built by a non-American maker, mostly Japanese brands, as opposed to Harley-Davidson or Indian.

A minibike is a small, low motorcycle with small wheels, usually for children, pit use or fun riding rather than public roads.

Momentum is the motion a bike carries from its mass and speed; keeping it steady helps heavy bikes float through sand and mud.

A monoshock is a rear suspension layout with a single shock absorber instead of a pair, often working through a linkage.

A motocross bike is a light, powerful off-road bike built for closed-circuit racing on dirt tracks with jumps.

Motorcycle brakes slow the bike by friction. Front and rear, disc and drum, hydraulic and cable systems explained.

Ergonomics is how well a motorcycle fits its rider: the position of seat, bars and footpegs and how easily the controls can be reached.

EU motorcycle licence categories are AM, A1, A2 and A, which differ by minimum age, engine size and power limits.

How to lift a fallen motorcycle with your legs and body position rather than your back, to avoid injury.

Motorcycle tyres are the only contact between bike and ground; their type, pressure and condition decide grip, handling and braking.

A motorcycle wheel holds the tyre and turns on the axle; it can be cast, spoked or forged, each with its own strengths and upkeep.

A motorcycle-specific cut means riding gear is shaped for the riding position, with pre-curved arms and legs and longer back panels.

The Nac Nac is a freestyle motocross trick where the rider swings one leg over the back of the bike in mid-air and remounts before landing.

A naked bike is a road motorcycle with little or no fairing, an upright riding position and the engine on show.

A nav tower is the frame behind a rally bike's screen that carries the roadbook holder, trip meters and the organiser's GPS.

A needle bearing is a roller bearing with long, thin rollers that carries high loads in a very small radial space.

In rallying, a neutralisation is a controlled zone or stop where race timing is frozen and riders must follow set rules.

A nyloc nut has a nylon insert that grips the bolt thread and stops the nut working loose from vibration.

An O-ring is a round rubber seal with a circular cross-section that seals joints against oil, fuel, coolant or air.

Octane rating measures a fuel's resistance to knocking; in Europe pumps show RON, such as 95 and 98.

The odometer records the total distance a motorcycle has travelled; trip meters show distance over shorter, resettable stretches.

OEM parts are the original parts fitted by the motorcycle manufacturer, as opposed to aftermarket replacements.

An off-camber turn or slope tilts away from the corner, so gravity pulls the bike towards the outside and reduces grip.

An off-road bike is a motorcycle built for unpaved terrain: gravel, forest trails, sand, mud and rocks.

An off-road helmet has a long chin bar and a sun peak but no face shield; it is worn with goggles.

An OHV pushrod engine has its camshaft low in the block, opening the overhead valves through pushrods and rocker arms.

Oil bath lubrication means a part runs partly or fully submerged in oil, as in enclosed chain cases and oil-bath air filters.

An oil cooler is a small radiator that cools engine oil with airflow, helping air-cooled and high-performance engines run cooler.

The oil filter traps wear particles and dirt from the engine oil; it is replaced at every or every second oil change.

Stopping with only one foot down, usually the left, so the right foot can stay on the rear brake pedal.

An open cradle frame has no tubes under the engine; the engine hangs from the frame and acts as a stressed or semi-stressed member.

An open-face helmet covers the top, back and sides of the head but has no chin bar, leaving the face exposed.

The opening vehicle drives a rally route ahead of competitors to check it; its changes appear in roadbook notes.

Overboring enlarges the cylinder bore, either to repair wear with an oversize piston or to increase engine capacity.

An overdrive gear turns the output shaft faster than the input shaft (ratio below 1:1), lowering engine revs at cruising speed.

An overhead cam engine has its camshaft in the cylinder head, driving the valves directly or via short rockers.

An oversquare engine has a bore larger than its stroke, allowing higher revs and bigger valves for more top-end power.

Oversteer is when the rear wheel loses grip before the front in a corner, so the tail slides out and the turn tightens.

The paddock is the area at a race track where teams park transporters, set up awnings and prepare and repair the bikes.

A paddock stand lifts the rear wheel by the swingarm using a lever, so you can clean and lube the chain or remove the wheel.

A panic rev is a burst of throttle in mid-air that lifts a nose-heavy bike's front end for a safer landing.

Panniers are luggage cases or bags mounted on each side of the rear wheel to carry gear on tours.

A parallel twin is a two-cylinder engine with both cylinders side by side, sharing one crankshaft.

Parc fermé is a closed area where competition bikes are held under the organiser's control and no work is allowed except as the rules permit.

Peg pressure is pushing down through the footpegs to steer, balance and settle the bike, especially when standing off-road.

A petcock is the fuel tap under the tank, with positions such as OFF, ON, RES (reserve) and sometimes PRI (prime).

Pillion means the passenger on a motorcycle, and also the passenger seat and footpegs.

A pinch flat happens when a hard impact squeezes the inner tube between the tyre and rim, leaving two small slits.

The piston moves up and down in the cylinder, turning combustion pressure into force on the crankshaft via the connecting rod.

The piston crown is the top face of the piston, forming the floor of the combustion chamber; its shape affects compression and combustion.

Piston rings seal the gap between piston and cylinder, holding compression and scraping oil off the cylinder wall.

A pit bike is a small dirt bike with 10–14 inch wheels and a simple 110–190 cc four-stroke engine, used for training and fun.

A pit board is a sign shown to a rider from the pit wall or trackside with position, gaps, laps left and instructions.

The pit lane runs beside the track for entering and leaving; the pits are the garages where the pit crew services the bikes.

Plastics are the bodywork panels of an off-road bike: mudguards, radiator shrouds, side panels and number plates.

A poker run is a social ride where participants visit checkpoints, draw a playing card at each and the best poker hand wins.

A positive camber turn is banked so its outside edge is higher than the inside, supporting the bike and adding grip.

Power delivery describes how an engine produces torque and power across the rev range and how the bike responds to throttle.

A power shift is changing gear without using the clutch, by briefly unloading the gearbox with the throttle.

The powerband is the rev range where an engine makes its most useful power; keeping it there gives the best acceleration.

The powertrain is everything that makes and delivers drive: engine, primary drive, clutch, gearbox and final drive to the rear wheel.

Pre-ignition is when the mixture ignites from a hot spot before the spark plug fires; it can quickly destroy a piston.

Preload is how much a suspension spring is compressed before load is applied; it sets sag and ride height, not spring stiffness.

The primary drive transfers power from the crankshaft to the clutch and gearbox, using gears, a chain or a belt.

A privateer is a racer without full factory backing who funds, prepares and often transports their own bike.

A production motorcycle is a model built in series and sold to the public, as opposed to a prototype or one-off racing bike.

PSI is an imperial pressure unit often used for tyre pressures; 1 bar is about 14.5 psi.

A quad is a four-wheeled ATV ridden astride with handlebars; in motocross the word also means a jump with four peaks in a row.

Qualifying decides which riders reach the final and where they start, using timed sessions or shorter heat races.

The quarter mile (402 m) and eighth mile (201 m) are standard drag racing distances, often used to compare motorcycle acceleration.

A quickshifter lets you change gear without the clutch: a sensor briefly cuts ignition or fuel so the gearbox can shift under load.

A radial tyre has carcass cords running across the tyre at about 90° to the direction of travel, with a belt under the tread for stability.

The radiator cools a liquid-cooled engine by passing hot coolant through thin tubes and fins where air carries the heat away.

Rain grooves are longitudinal channels cut into concrete roads for drainage; they can make a motorcycle feel loose and twitchy.

Rainbow-coloured patches on a wet road show spilled oil or fuel and warn of a very slippery surface for motorcyclists.

Rake is the angle of the steering axis from vertical; a steeper rake gives quicker steering, a longer rake more straight-line stability.

A motorcycle rally is a long-distance off-road race navigated with a roadbook; the word also means a social gathering of riders.

The French abbreviations used in rally-raid roadbooks: stage start DSS, neutralisation DN/FN, transfer DT/FT, speed zones DZ/FZ and D/G for right/left.

Rally roadbooks use French words: piste (dirt track), ornières (ruts) and oued (dry riverbed, wadi).

Rally waypoints are GPS points riders must pass to validate the route; types such as WPV, WPM, WPE and WPS differ in how much GPS guidance you get.

Reaction time is the delay between seeing a signal or hazard and acting on it; in drag racing it is measured from the green light.

Dragging the rear brake lightly against throttle and clutch stabilises the bike in slow turns, U-turns and tight manoeuvres.

A rear wheel drift is a controlled sideways slide of the rear tyre in a corner while the front tyre keeps grip.

Rebound damping controls how fast the fork or shock extends again after compressing, keeping the tyre in contact with the ground.

The redline is the maximum safe engine speed, marked in red on the rev counter; a rev limiter usually stops the engine going past it.

A relay is an electrically operated switch: a small control current switches a larger current for parts such as the starter, lights or fuel pump.

Revalving means changing the shim stacks and valves inside a fork or shock to alter its damping for rider weight and use.

Revving means opening the throttle in a quick burst to raise engine speed, for example to match revs on a downshift.

A rhythm section is a run of closely spaced jumps on a motocross or supercross track that riders clear in different combinations.

A rich mixture contains more fuel than the ideal air-fuel ratio; symptoms include black plug, sooty exhaust, poor economy and bogging.

The ride captain leads a group ride, sets the pace and route and gives signals that are passed back through the group.

Ride modes are electronic presets that change throttle response, power, traction control, ABS and sometimes suspension for different conditions.

A riders' meeting is a briefing before a race or group ride covering the schedule, route, flags, safety rules and changes.

Riding gear is the protective clothing a motorcyclist wears: helmet, jacket, trousers, gloves and boots, ideally with certified armour.

Riding two-up means carrying a passenger; it changes braking, handling and suspension needs, so preload and tyre pressure often need adjusting.

A rigid frame has no rear suspension: the rear axle is fixed directly to the frame, as on early motorcycles and many custom choppers.

Road crown is the slight arch of a road from the centre to the edges so water drains off; it affects lean and grip in corners.

Road rash is skin abrasion from sliding on tarmac after a fall; abrasion-resistant gear greatly reduces it.

Road snakes are strips of bitumen sealant used to fill road cracks; they become slippery when hot or wet.

A roadbook is the rally navigation document: numbered boxes with distances, tulip diagrams and notes describing the route step by step.

Each roadbook box has total and partial distance, a tulip diagram and a notes column with symbols, CAP headings and dangers.

Rally roadbooks mark hazards with one, two or three exclamation marks: caution, slow down, or serious danger.

Roadbook distances point to an exact feature, and small errors (trip drift) build up; here is how to keep your trip meter in line with the roadbook.

A roadbook holder scrolls the rally roadbook on the handlebars; a bar-mounted remote moves it and resets or corrects the trip meter.

How to read a rally roadbook tulip: the entry ball shows where you arrive, the arrow where to leave, CAP the compass heading, dashes open terrain.

A rock garden is a trail section full of loose and fixed rocks of different sizes, ridden with careful line choice, balance and momentum.

A rocker arm is a pivoting lever in the cylinder head that transfers motion from the camshaft or pushrod to open the valve.

Roll-offs are a goggle system with a clear film wound between two canisters; pulling a cord moves fresh film across the lens to clear mud.

A roll-up is a trials and enduro technique for climbing onto an obstacle using a short burst of throttle and the bike's momentum.

A roller is a smooth, rounded mound on a motocross or supercross track that can be jumped or rolled over.

A rolling chassis is a motorcycle frame with suspension and wheels fitted, able to roll, but usually without engine or bodywork.

Rolling on means opening the throttle smoothly and progressively, which settles the suspension and gives the best grip when accelerating.

RPM means revolutions per minute: how many times the crankshaft turns each minute. 'Revs' is the everyday word for engine speed.

A rubber-mounted engine sits on rubber bushes to isolate vibration; a solid-mounted engine is bolted directly to the frame.

Running out of tyre means leaning beyond the tread edge so the sidewall touches the road and grip suddenly disappears.

Ruts are deep grooves worn into a track or trail by repeated passes; riding them well means committing, looking ahead and staying centred.

SAE is the US engineering society behind the viscosity grades on oil labels, such as 10W-40; motorcycle oil also needs a JASO rating.

Sag is how far the suspension compresses under the bike's own weight and the rider; setting it correctly is the first step of suspension setup.

Riding in soft sand needs momentum, a light front end and weight back; sand pits and sandy trails punish hesitation.

The Schrader valve is the standard spring-loaded tyre valve on motorcycles, also used on air forks and shocks.

A scooter is a step-through two-wheeler with a floorboard, small wheels and usually an automatic CVT; riders also call any bike a 'scoot'.

A scrambler is a road bike with off-road styling: high bars, dual-purpose tyres and often a high exhaust; the name comes from early scrambles racing.

Seat bounce is a jump technique: the rider sits down hard on the take-off to compress the suspension and get extra lift.

Selector forks sit inside the gearbox and slide gears along their shafts to engage each gear, guided by the shift drum.

A sending unit is a sensor that measures something such as fuel level, temperature or oil pressure and sends a signal to a gauge or ECU.

Shaft drive sends power to the rear wheel through a driveshaft and bevel gears instead of a chain or belt: clean and low-maintenance but heavier.

A shim is a precisely sized thin disc or plate used to set clearances, for example valve clearance on bucket-type valve trains.

A shock absorber combines a spring and a hydraulic damper; the spring carries the load and the damper controls motion by forcing oil through valves.

Short shifting means changing up early, well before peak power, to ride smoothly, save fuel or keep traction on slippery ground.

Shotgun pipes are a twin exhaust style with two parallel pipes ending side by side, like a double-barrelled shotgun; popular on V-twin customs.

Shovelhead is the nickname of the Harley-Davidson big twin built from 1966 to 1984, named after rocker covers that look like upturned shovels.

The side-saddle mount is a way to get on a tall bike: sit sideways on the seat from the left, then swing the leg over or bring legs into position.

A sidecar is a one-wheeled car attached to the side of a motorcycle to carry a passenger or load, creating a three-wheeled outfit.

The sidestand is the fold-out leg on the left side that holds a parked bike; most bikes have a switch that stops the engine if you ride off with it down.

A silencer, or muffler, is the end part of the exhaust that reduces noise; it also shapes back pressure and power delivery.

Singletrack is a narrow trail wide enough for only one bike at a time, typical of enduro and forest riding.

SIPDE stands for Scan, Identify, Predict, Decide, Execute, a five-step hazard-awareness method taught in US rider training.

A sissy bar is a tall passenger backrest frame behind the pillion seat, common on cruisers and choppers; it can also hold luggage.

Skimming is riding fast across a whoops section so the wheels touch only the tops of the bumps, keeping the bike level.

A slave cylinder is the hydraulic piston unit that receives pressure from the master cylinder and operates the clutch.

A slick is a racing tyre with no tread pattern for maximum dry grip on track; the word also describes a road tyre worn bald.

A slip-on is an aftermarket silencer that replaces only the end can, sliding onto the standard header pipes or link pipe.

Slop is unwanted play or looseness in a component, such as worn bearings, linkages or cables; it reduces precision and warns of wear.

A slow race is a balance contest where the last rider to cross the line without putting a foot down wins; great clutch and balance practice.

Softail is Harley-Davidson's frame design that hides the rear shock under the bike so it looks like a rigid hardtail but has rear suspension.

SOHC means one camshaft in the cylinder head per bank of cylinders, operating both intake and exhaust valves, often via rocker arms.

A solenoid is a coil that acts as an electromagnet; on motorcycles the starter solenoid switches the high current that turns the starter motor.

The spark plug creates the spark that ignites the fuel-air mixture in the combustion chamber; its colour also reveals how the engine is running.

A speed wobble is a sudden, violent side-to-side oscillation of the handlebars; also called shimmy or tank slapper.

A splat is a trials and hard enduro technique where the rear wheel is driven into the face of a high obstacle to bounce the bike up onto it.

Spokes are the tensioned steel rods that connect the hub to the rim on a wire-spoked wheel; they need regular tension checks.

A sport bike is a road-legal motorcycle derived from racing, with full fairing, a forward riding position and engines tuned for high revs.

A sport tourer combines sport bike performance with touring comfort: a more upright position, wind protection and luggage options.

Spring rate is a spring's stiffness, given in N/mm (or kg/mm): how much force is needed to compress it by one millimetre.

A springer fork is a vintage front suspension design with exposed springs and a separate sprung leg that moves the wheel on short links.

Sprockets are toothed wheels on the gearbox output (front) and rear wheel (rear) that drive the chain; tooth count sets the final gearing.

Squaring off means braking deep, turning sharply at a late apex and getting the bike upright early to accelerate hard out of the corner.

Squat is the rear of the bike sinking under acceleration as weight transfers backwards; chain and swingarm geometry can resist it (anti-squat).

A standard is a no-frills, all-round road bike with an upright riding position, flat seat and pegs under the rider; sporty versions are called naked bikes.

Standing on the pegs with knees and elbows bent lets the legs absorb bumps and the bike move freely; the basic off-road riding position.

The start gate is the row of metal gates that drop to start a motocross or supercross race; good gate technique is key to a strong start.

The starter motor is an electric motor that cranks the engine; a relay switches it and a sprag clutch transfers the drive.

Static balance is keeping a motorcycle upright while stopped or nearly stopped using small body and steering inputs, as in trials track stands.

A steering damper is a hydraulic unit between frame and fork that resists fast steering movements to prevent speed wobbles and kickback.

Steering geometry is the relationship of rake, trail, wheelbase and offset that decides how quickly and stably a motorcycle steers.

The steering head is the frame tube the fork pivots in; its bearings let the fork turn smoothly and must be free of play and notches.

A steering lock fixes the fork at full left or right lock with the ignition key, making a parked bike harder to wheel away.

A step-down is a jump where the landing is lower than the take-off; in a rally roadbook it marks a sudden drop in the terrain.

A step-up is a jump where the landing is higher than the take-off; in a rally roadbook it marks a sudden ledge up in the terrain.

Stiction is static friction in fork and shock seals and bushes that stops the suspension reacting smoothly to small bumps.

A stock motorcycle is exactly as it left the factory, with original (OEM) parts and settings and no aftermarket modifications.

A stoppie is a stunt where hard front braking lifts the rear wheel and the bike balances on its front wheel; the opposite of a wheelie.

Straight pipes are exhausts with no baffles or silencing, making the bike extremely loud and illegal for road use in the EU.

A streetfighter is a sport bike stripped of its fairing, usually with a wide handlebar and aggressive styling; also called a hooligan bike.

A stressed member is a component, usually the engine, that forms a load-bearing part of the frame instead of just being carried by it.

A stretched bike has a longer front fork, more rake or an extended swingarm; used on choppers for looks and on drag and hill climb bikes for stability.

Stroke is the distance the piston travels from top to bottom dead centre; together with bore it sets engine capacity. Also used for suspension travel.

A suicide shift is an old setup with a foot clutch and hand gear lever on the tank, forcing the rider to take one hand off the bars to change gear.

The sump is the oil reservoir at the bottom of the engine; wet-sump engines store oil there, dry-sump engines keep it in a separate tank.

A superbike is a top-level sport bike, usually around 1000 cc, and the name of the World Superbike racing class for production-based machines.

A supercharger, or blower, is a crank-driven compressor that forces extra air into the engine. Boost is the pressure it adds.

Supercross (SX) is motocross on tight man-made tracks, usually in stadiums, with big jumps, rhythm sections and whoops.

Supermini is a youth motocross class for big-wheel 85 cc two-strokes and up to around 112–150 cc machines, between 85 cc and full-size bikes.

Supermoto is a dirt bike with 17-inch road wheels, sticky tyres and big brakes, and a racing style that mixes tarmac with a dirt section.

Supersport describes mid-size sport bikes, traditionally 600 cc four-cylinders, and the racing class built around them.

Suspension is the system of springs, dampers and linkages that lets the wheels move relative to the frame and keeps the tyres in contact with the ground.

Suspension travel is how far the fork and rear wheel can move up and down; long travel absorbs big bumps, short travel suits road riding.

The sweep is the experienced rider at the back of a group ride who watches the group and helps anyone who stops or has a problem.

The swingarm is the pivoting arm that holds the rear wheel and connects it to the frame, working with one or two shocks.

A switchback is a sharp hairpin bend on a road or trail zig-zagging up or down a steep slope.

T-CLOCS is a pre-ride checklist from the US Motorcycle Safety Foundation: Tyres, Controls, Lights, Oil, Chassis, Stands.

A tabletop is a motocross jump with a flat top instead of a gap, so short landings are forgiving. It also names a flattened-bike jump trick.

The tachometer, or tach, shows engine speed in revolutions per minute (rpm) and marks the redline you should not exceed.

A tail bag is luggage that fastens to the pillion seat or rear rack, adding storage without fitting hard cases.

The tail gunner, or sweep, rides last in a group ride, watches the group from behind and helps anyone who stops or breaks down.

Tall gearing means a lower final drive ratio: the engine turns fewer rpm per km/h, giving higher top speed but softer acceleration.

A tank bag sits on top of the fuel tank, keeping essentials, maps or a phone within reach while you ride.

A tank slapper is a violent, fast oscillation of the handlebars from lock to lock, the most extreme form of speed wobble.

A tappet is the part between the cam and the valve that passes the cam's push to the valve. Hydraulic tappets adjust clearance themselves.

Target fixation is staring at a hazard you want to avoid, which makes you steer straight into it. Look where you want to go instead.

TDC, top dead centre, is the point where the piston is at its very top in the cylinder; it is the reference for ignition and valve timing.

Tear-offs are thin clear films stacked on a goggle lens; when mud covers your view you pull one off to see again.

Technical terrain is off-road ground with rocks, roots, steps or tight turns that demands precise control, balance and line choice.

Telescopic forks are the most common motorcycle front suspension: two sliding fork legs with springs and oil damping inside.

Textile riding gear is jackets, trousers and suits made from synthetic fabrics instead of leather, usually with CE armour and weather protection.

A TFT display is a colour screen used in modern motorcycle dashboards, clearer and more flexible than older segment LCDs.

A triple is a three-cylinder engine, usually inline, combining much of a twin's low-down torque with a four's smooth top end.

The throttle controls engine power: the twist grip opens a valve or slide that lets more air, and with it fuel, into the engine.

The throttle body is the fuel-injection equivalent of a carburettor: it houses the throttle valve, often the injector and a position sensor.

Throttle control is opening and closing the throttle smoothly and precisely to manage power, grip and the bike's balance.

A throttle lock or rocker is a simple accessory that holds the throttle steady or lets you push it with your palm, easing fatigue on long rides.

A time control is a rally or enduro checkpoint where you must check in at your assigned minute; arriving late, and often early, costs penalties.

The top end is the upper part of an engine: piston, rings, cylinder, head and valve gear. It can also mean a bike's top speed or the high-rpm range.

Torque is the twisting force an engine produces, measured in newton-metres (Nm); together with rpm it determines power.

A torque wrench tightens bolts to an exact torque setting in Nm, so parts are neither loose nor overtightened and damaged.

Torx is a six-point star-shaped screw drive that grips better than Phillips or flat-blade heads and is less likely to cam out or strip.

Total distance is the large number in a rally roadbook box: the cumulative distance from the start of the section, matched against your trip meter.

A touring bike, or tourer, is built for long-distance travel, with wind protection, comfortable seating, luggage and a large fuel range.

In rally roadbooks, a trace is a faint vehicle track, less defined than a piste, that may be hard to see on the ground.

Traction is the grip between tyre and surface that lets a bike accelerate, brake and corner; it depends on tyres, surface, load and rider input.

Traction control detects rear-wheel spin and reduces engine power to keep the tyre gripping, especially on slippery surfaces.

Trail is the distance on the ground between the steering axis and the tyre contact patch; more trail means more stability, less quick steering.

Trail braking means braking into a corner and gradually releasing the brake as lean angle increases, to keep the front loaded and tighten the line.

The transmission carries engine power to the rear wheel: primary drive, clutch, gearbox and final drive by chain, belt or shaft.

Trap speed is a bike's speed as it crosses the finish line of a drag strip, measured over a short timed section at the end.

The tread pattern is the design of grooves or knobs on a tyre; it clears water, mud or sand and decides what surfaces the tyre suits.

Trials is a sport of riding over obstacles without putting a foot down, on very light bikes with low gearing and almost no seat.

A trike is a three-wheeled motorcycle without a sidecar, with two wheels at the rear or, in a reverse trike, two at the front.

Triple clamps, also called triple trees or yokes, hold both fork legs and the steering stem together and set the fork offset.

A tripmeter is a resettable distance counter showing kilometres since the last reset; useful for fuel planning and rally navigation.

Troubleshooting is the systematic search for the cause of a fault, starting with the simplest checks: fuel, spark, air, compression.

Tucking in means crouching low behind the screen, elbows and knees in, to cut wind drag at high speed or on a straight.

A tulip is the small drawing of a junction in a rally roadbook box; you read it from the dot where you arrive to the arrow where you leave.

Twin-shock rear suspension uses two shock absorbers, one each side of the swingarm; classic layout still used on cruisers, scooters and retro bikes.

A two-into-one exhaust joins the header pipes of a twin-cylinder engine into one pipe and silencer, saving weight and often boosting midrange.

The two-second rule: keep at least two seconds between you and the vehicle ahead, counted from a fixed landmark; more in rain or darkness.

A two-stroke engine completes a power cycle in two piston strokes (one crank turn); it is light and punchy and common in motocross and enduro.

A two-wheel drift is a controlled slide in which both tyres slip sideways through a corner; an advanced racing and flat-track skill.

Aspect ratio is the tyre sidewall height as a percentage of its width, the middle number in a size like 180/55 ZR17.

The bead is the wire- or fibre-reinforced inner edge of a tyre that seals and locks it onto the rim. Seating and fitting tips.

A tyre mousse is a foam insert that replaces the inner tube in off-road tyres, making them puncture-proof.

Tyre pressure affects grip, handling, wear and safety; always check it cold and set it to the manufacturer's recommendation.

Most motorcycle tyres must be fitted so they roll in the direction of the arrow on the sidewall; fitting them backwards hurts grip and wear.

Underbraking is not using the brakes fully in an emergency, so the bike stops later than it could; practise hard braking to avoid it.

An undersquare or long-stroke engine has a stroke longer than its bore; it favours low-rev torque over high-rev power.

A universal joint lets a drive shaft turn through an angle; it is used in shaft-drive motorcycles and ATV propshafts.

Unsprung weight is the mass not carried by the springs: wheels, tyres, brakes and part of the fork and swingarm. Less of it means better grip.

An upshift is changing to a higher gear; on most motorcycles you lift the gear lever, briefly easing the throttle or using the clutch or a quickshifter.

Upside-down forks have the thick outer tubes clamped at the top and the thin stanchions at the bottom; stiffer and with less unsprung weight.

A UTV, or side-by-side, is a steering-wheel off-road vehicle where driver and passenger sit next to each other inside a roll cage.

A V-twin is a two-cylinder engine with cylinders in a V; known from Harley-Davidson cruisers, Ducati's L-twins and Moto Guzzi's transverse twins.

A V4 is a four-cylinder engine with two pairs of cylinders in a V; it is compact and powerful, used in sports bikes and big tourers.

Valve clearance is the small gap in a four-stroke valvetrain that lets parts expand with heat and ensures valves close fully. Check it regularly.

Valve guides are tubes pressed into the cylinder head that keep each valve moving straight; worn guides cause oil burning and poor sealing.

The valvetrain opens and closes an engine's valves in time with the piston: camshafts, their drive, tappets or rockers, springs and the valves.

Vapour lock is when fuel boils in the lines or carburettor because of heat, blocking fuel flow so the engine stalls or will not restart.

Vespa is the Italian scooter brand made by Piaggio since 1946, famous for its steel monocoque body and iconic design.

The VIN is a unique 17-character code stamped on the frame that identifies a motorcycle; always check it against the papers when buying used.

Viscosity is how thick a fluid is and how easily it flows; oil grades like 10W-40 describe viscosity cold and at operating temperature.

Visual scanning is constantly sweeping your eyes far ahead, near and to the sides to spot hazards early and plan lines and inputs in time.

The regulator-rectifier converts the alternator's AC to DC and limits charging voltage, protecting the battery and electrics. A common failure part.

Washboard, or corrugations (tôle ondulée in rally roadbooks), is a rippled surface across a dirt road that shakes the bike and reduces grip.

A washout is a channel or hole on a trail cut by flowing water; it can be deep and hard to see, so slow down and choose your line carefully.

A water crossing means riding through a stream, river or flooded trail; check depth, current and bottom first, and protect the air intake.

A waypoint is a location saved as GPS coordinates, used to mark destinations, junctions, fuel stops or points of interest on a route.

Weight transfer is the shift of load between the wheels: braking moves weight to the front, acceleration to the rear, changing grip at each end.

Wheelbase is the distance between the front and rear axles; a longer wheelbase adds stability, a shorter one makes a bike more agile.

A wheelie is riding on the rear wheel only with the front wheel lifted; a stunt, but also a useful off-road skill for clearing obstacles.

A wheelie bar is an extension with small wheels behind a drag bike's rear wheel that stops the front lifting too high or the bike flipping at launch.

Wheelspin is when the driven rear wheel turns faster than the bike is moving; useful in small doses off-road, but it costs grip and can dig in sand.

A whip is a motocross jump style where the rider kicks the rear of the bike sideways in mid-air and straightens it before landing.

A white flag's meaning depends on the series: last lap in motocross and many national series, a slow vehicle on track in FIM road racing.

Whoops are a row of closely spaced bumps on a motocross or enduro track; fast riders skim across the tops, slower riders roll through them.

The windward slope is the side of a dune facing the wind: usually gentle and firmer, while the leeward side behind the crest can be steep and soft.

WOT, wide open throttle, means the throttle fully open: the engine makes maximum power for its current revs. Used in testing and tuning.

An X-ring chain is a sealed drive chain whose X-section seals keep grease in and dirt out with less friction than O-rings, so it lasts longer.

The yellow flag with red vertical stripes warns of reduced grip on that part of the track, such as oil, water or debris.

A yellow flag signals danger ahead: slow down, be ready to stop and do not overtake until you have passed the incident.

A zap is a trials and hard-enduro technique for climbing big steps: like a double blip, but you dump the clutch on the second blip for extra rear lift.