ITI/NCVT Mechanic Motorcycle (AITT Theory) cheat sheet

Personal protective equipment hierarchy: eliminate the hazard first, then substitute, then engineer controls (guards, fume extraction), then administrative controls, then PPE as the last line of defence.

Petrol (flash point about -43 °C) ignites from static, hot exhaust or a spark; no smoking, no naked flame and no mobile phones within 5 m of fuel handling; bond and earth containers before decanting.

Carbon monoxide from petrol engines is odourless and binds haemoglobin about 200-250 times more strongly than oxygen; never run an engine in an enclosed bay without forced ventilation and CO monitoring.

Battery charging releases hydrogen; keep vents open, no sparks, and top up with distilled water only after charging, since electrolyte level rises during charge.

Electrolyte (about 35 % sulphuric acid) burns: flush skin or eyes with copious water for at least 15 minutes and refer for medical attention; neutralise spills with sodium bicarbonate.

Manual handling rule: keep the load close, back straight, lift with the legs, and get help above about 25 kg; a motorcycle engine or frame is a two-person lift.

Fire classes: Class A solids (water), Class B flammable liquids (foam, dry powder, CO2), Class C gases, Class D metals; electrical fires need CO2 or dry powder, never water.

Compressed air for cleaning must be below about 2 bar (30 psi) with a chip guard; never point it at skin - an air embolism can be fatal.

Spanner sizing refers to the across-flats dimension of the nut, not the thread size; a 13 mm spanner fits a nut measuring 13 mm across flats.

Six-point sockets grip flats and resist rounding; twelve-point sockets give swing clearance but are for undamaged fasteners only.

Torque wrench types: click (setting must be backed off to zero after use), beam (no setting needed, read at the pointer), and electronic; never use a torque wrench to loosen.

A screwdriver tip must match the slot width and thickness; a loose fit cams out, damages the head and can cause a hand injury.

Files cut on the forward stroke only; the correct pressure is applied on push and released on return, and soft metals are cleaned with a file card.

Hacksaw blade: 18 teeth per inch for thick sections and soft metals, 24-32 TPI for thin tube and hard metals; at least three teeth must be in contact with the work.

Chisels and punches are mushroom-headed when worn; grind off the burr at about 60 degrees, because a split head can send a fragment into the eye.

Feeler gauges measure gaps by trial: the correct blade drags slightly; never force a blade, since bending it destroys the calibration.

Vernier caliper reading = main scale value + (coinciding vernier line × least count); least count = 1 main scale division / number of vernier divisions, typically 0.02 mm for a 50-division scale.

Micrometer least count = pitch / thimble divisions; a 0.5 mm pitch with a 50-division thimble gives 0.01 mm, and the reading is barrel + thimble + zero error correction.

Zero error: if the vernier or thimble zero lies to the right of the datum the error is positive and is subtracted from the reading; negative error is added.

Micrometer reading = barrel sleeve value + (thimble division × least count); check the zero with the anvils closed and clean before use.

Dial gauge (DTI) measures runout, end play and flatness; magnetic base holds it, and the plunger must be perpendicular to the surface being checked.

Cylinder bore is measured with a bore gauge or inside micrometer at three heights and two planes (parallel and perpendicular to the crankshaft) to detect taper and out-of-round.

Torque conversion: 1 kgf·m = 9.81 N·m; 1 N·m = 0.738 lbf·ft; 1 inch = 25.4 mm; 1 thou = 0.0254 mm.

Vernier calipers are for outside, inside and depth measurement; a micrometer is for outside dimensions only and must not be used on a rotating workpiece.

Plain carbon steel classification by carbon content: low carbon (mild) up to 0.3 % C, medium 0.3-0.6 % C, high carbon 0.6-1.4 % C; hardness and strength rise with carbon while ductility and weldability fall.

Cast iron contains 2-4 % carbon and is brittle in tension but good in compression and damping; it is used for cylinder liners and machine bases.

Alloy steels add elements for properties: chromium for hardenability and corrosion resistance, nickel for toughness, molybdenum for high-temperature strength, vanadium for fine grain.

Aluminium alloy is about one-third the density of steel with good heat conduction, which is why pistons and cylinder heads are aluminium; it needs iron or chrome liners/plating for wear surfaces.

Case hardening (carburising) hardens a low-carbon surface while keeping a tough core; induction and flame hardening harden selected surface areas of medium-carbon steel.

Heat treatment: annealing softens and relieves stress; normalising refines grain; hardening (quench) followed by tempering restores toughness lost in the quench.

Gasket materials: copper and aluminium for high-temperature joints (cylinder head, exhaust), fibre/paper for low-pressure oil and water joints, O-rings for pressurised fluid sealing.

Non-ferrous identification: aluminium is light and non-magnetic, copper/brass is reddish-yellow, and a magnet test quickly separates ferrous from non-ferrous parts.

Thread designation M10 × 1.5 means metric thread, 10 mm nominal major diameter, 1.5 mm pitch; a fine series such as M10 × 1.25 has a smaller pitch and greater self-locking tendency.

Unified thread: a 5/16-18 UNC has 18 threads per inch (coarse), while 5/16-24 UNF is the fine series; thread pitch in mm = 25.4 / TPI.

Torque produces clamping force: T = K × F × d, where K is the nut factor (about 0.2 dry steel), F is the preload and d the nominal diameter; lubricated threads need lower torque.

Torque sequence for a cylinder head is from the centre outwards in two or three stages, and some engines require a final angle (torque-to-yield) turn; stretch bolts are single-use.

Grade markings: metric property class 8.8 means 800 MPa tensile and 0.8 of yield ratio; 10.9 and 12.9 are higher grades; use the grade specified, never a lower one.

Locking methods: split pin with castellated nut, tab washer, spring washer, thread-locking fluid (medium for serviceable, high-strength for permanent), and nylon-insert lock nuts.

Fit types: clearance fit (shaft smaller than hole, e.g. H7/g6 for a sliding bearing), interference fit (shaft larger, needs press or heat), transition fit (either, located by other means).

Hole-basis system: the hole is H (lower deviation zero) and the shaft letter gives the fit; a capital letter denotes the hole, a lower-case letter the shaft.

Four-stroke cycle: intake, compression, power (combustion) and exhaust, two crankshaft revolutions per cycle; a two-stroke completes the cycle in one revolution with transfer and scavenging ports.

Compression ratio = (swept volume + clearance volume) / clearance volume; a higher ratio raises thermal efficiency but requires higher-octane fuel to avoid detonation.

Swept volume of one cylinder = (π/4) × bore² × stroke; engine capacity = swept volume × number of cylinders.

Valve timing: intake opens before TDC and closes after BDC; exhaust opens before BDC and closes after TDC; valve overlap improves scavenging at speed.

Valve clearance is set cold on most engines between the cam and follower (or rocker and valve stem); too little clearance causes burning or compression loss, too much causes noise and reduced lift.

Mean piston speed = 2 × stroke × rpm / 60; it is a better indicator of engine stress than rpm alone.

Firing order and interval: a 4-cylinder 4-stroke fires every 180° of crank rotation; a single-cylinder 4-stroke fires once every 720°.

Two-stroke crankcase is part of the induction path, so crank seals must be airtight; a leaking seal leans the mixture and can seize the piston.

Stoichiometric air-fuel ratio for petrol is about 14.7:1 by mass; rich mixtures (about 12.5:1) give maximum power, lean mixtures give economy but risk detonation and overheating.

Octane number rates anti-knock quality; higher compression or turbocharged engines need higher octane; cetane number applies to diesel and rates ignition quality.

Carburettor circuits: float chamber (level), pilot/idle, needle jet and jet needle, main jet, throttle slide, choke/enricher and accelerator pump; the main jet controls near-full throttle.

Electronic fuel injection uses sensors (MAP, TPS, ECT, IAT, oxygen/lambda, crank position) and the ECU calculates injection duration; a lambda value of 1.00 means stoichiometric.

Ignition coil steps battery voltage up to several thousand volts; the spark occurs at the plug gap (typically 0.6-0.9 mm), and ignition timing is advanced with engine speed.

Spark plug heat range: a hot plug has a long insulator nose and runs hotter; a cold plug has a short nose and dissipates heat faster; the plug must match the engine's heat load.

Lubrication: pump delivers oil to the filter, main gallery, crankshaft and camshaft; oil performs lubrication, cooling, cleaning and sealing; viscosity is graded by SAE (e.g. 10W-40).

Cooling: liquid system uses a thermostat, radiator, water pump and pressure cap (about 1.1-1.3 bar) to raise boiling point; air-cooled engines rely on fins and a rich mixture for cooling.

Primary drive reduces crankshaft speed to the clutch/gearbox input; overall ratio = primary ratio × gearbox ratio × final drive ratio.

Clutch operation: the pressure plate clamps the friction plates against the steel plates; the release mechanism lifts the pressure plate to disengage, and free play at the lever prevents slip.

Wet multiplate clutch runs in engine oil; use only the specified oil, because friction modifiers in car oils can cause clutch slip.

Constant-mesh gearbox: gears are always in mesh, and sliding dogs or shift forks select which pair drives the shaft; a bent shift fork causes gear jumping or missed shifts.

Final drive types: chain (about 2-3 % loss, needs slack and lubrication), belt (quiet, needs tension and alignment), shaft (sealed, needs hypoid oil in the bevel box).

Chain slack is set with the bike on the side stand or as specified (typically 20-30 mm); too tight damages output shaft bearings, too loose risks derailment.

Sprocket ratio = rear teeth / front teeth; fitting a larger rear or smaller front sprocket lowers top speed and raises acceleration.

V-belt CVT (scooter) ratio changes with roller weights and the torque spring; worn rollers or a glazed belt cause poor acceleration and belt slip.

Frame types: cradle (single or double), trellis, twin-spar aluminium and backbone; the frame carries engine, suspension and steering loads and must align the steering head with the swingarm pivot.

Rake (caster) angle and trail: trail = (R × cos rake) − offset, where R is wheel radius; more trail increases straight-line stability, less trail quickens steering.

Telescopic fork: spring supports load, damper controls rebound and compression; fork oil level and viscosity change damping, and unequal oil levels cause handling pull.

Swingarm and monoshock: preload sets ride height/sag, rebound controls how fast the spring extends, compression controls how fast it compresses; static sag is typically 25-35 mm.

Wheel balance: static imbalance shows as a heavy spot; dynamic imbalance causes wheel shimmy; balance with the tyre fitted and the axle supported on stands.

Spoked wheel truing: radial runout is corrected by tightening/loosening spokes evenly, lateral runout by pulling the rim to one side; check runout with a dial gauge.

Steering head bearings: too loose causes shimmy and knocking, too tight causes weave and notchy steering; adjust to zero play with the front wheel off the ground.

Wheel bearing play is checked with the axle clamped and the rim rocked; any detectable play or roughness means replacement, not adjustment.

Hydraulic brake: force at the caliper = pedal force × pedal ratio × (caliper piston area / master cylinder area); a larger master cylinder gives a firmer, shorter travel lever.

DOT brake fluid is hygroscopic; DOT 3/4 are glycol-based and absorb water, lowering the boiling point, so they are replaced periodically; DOT 5 silicone must not be mixed with glycol fluid.

Brake fade is caused by heat (fluid boiling or pad outgassing); a spongy lever indicates air in the system, and bleeding removes it.

Disc brake minimum thickness is stamped on the disc; pads are replaced when friction material reaches the wear limit (about 1 mm) or is contaminated with oil.

Tyre markings: 120/70-17 means 120 mm section width, 70 % aspect ratio, 17 inch rim; the load index and speed symbol follow, e.g. 58H.

Tyre pressures are set cold; under-inflation increases rolling resistance, heat and shoulder wear; over-inflation wears the centre and reduces grip.

Wheel alignment: front and rear wheels must share the same centre line; misalignment shows as uneven tyre wear and a bike that pulls to one side; check with string lines or a straight edge.

Tread wear indicators show the minimum depth (about 1.6 mm for motorcycles in many jurisdictions); replace tyres with cuts, bulges or exposed cords.

Ohm's law: V = I × R; power P = V × I = I²R = V²/R; a 12 V, 60 W headlamp draws 5 A.

Series circuit: current is common, voltages add, total resistance adds; parallel circuit: voltage is common, currents add, total resistance is less than the smallest branch.

Lead-acid battery: each cell about 2.1 V, so a 12 V battery has six cells; open-circuit voltage of about 12.6-12.8 V indicates full charge, below 12.0 V is discharged.

Charging system: alternator output is rectified and regulated to about 13.5-14.5 V at the battery; a low reading indicates a faulty regulator, stator or wiring.

Starter circuit: battery, main fuse, starter relay/solenoid, starter motor and earth; a click with no crank points to a flat battery, bad earth or solenoid contacts.

Ignition and sensors: a pickup coil or crank sensor gives the ECU the position signal; a faulty sensor causes no-spark or poor running, and the ECU stores a fault code.

LED and electronic loads are polarity sensitive; a CAN-bus or ECU-controlled lighting circuit may not accept a plain bulb substitution without a load resistor.

Fuse rating protects the wiring, not the device; replace with the same rating, because a higher fuse allows the harness to overheat and burn.

Diagnostic sequence: verify the complaint, gather symptoms, check the basics (fuel, spark, compression, air), then test components; do not replace parts without a test result.

Compression test: throttle wide open, engine warm, all plugs out; a reading below specification or a large variation between cylinders indicates ring, valve or head gasket trouble.

Leak-down test pressurises the cylinder at TDC; air from the exhaust means exhaust valve leak, from the intake means intake valve leak, from the crankcase means rings, and bubbles in the radiator mean a head gasket.

Spark test: hold the plug against earth with a known-good plug and check for a strong blue spark; a weak yellow spark suggests coil, plug cap or battery voltage problems.

Fuel system check: confirm pump delivery and pressure, then injector pulse; a blocked filter or failing pump causes lean running and power loss.

Service intervals are set by the manufacturer; typical items are engine oil and filter, air filter, valve clearance, chain adjustment, brake fluid and tyre pressures.

Torque and sequence: use the specified torque and sequence for cylinder heads, wheel axles and brake calipers; recheck after the first ride.

Road test after repair: check brakes, steering, lights, leaks and unusual noise before returning the machine; record the work performed and parts used.

Taper and out-of-round calculation: taper = (top diameter − bottom diameter) / height; out-of-round = maximum diameter − minimum diameter measured at 90°.

Piston-to-bore clearance is measured with the piston at a specified height from the skirt and the feeler gauge or micrometer; too little clearance causes seizure.

Ring end gap is checked with the ring squared in the bore using a piston; too small a gap causes ring breakage when hot.

Surface finish and flatness of a cylinder head are checked with a straight edge and feeler gauge; warpage beyond the limit requires resurfacing or replacement.

Bearing clearance is measured with Plastigauge: the crushed strip width is compared with the scale, and the reading must fall within the manufacturer's range.

Runout limits: wheel and disc runout are checked with a dial gauge; a warped disc causes pulsation at the lever and must be replaced, not machined beyond the limit.

Thread repair: a stripped thread is restored with a helicoil or thread insert of the same nominal size, and the repair must not reduce the parent material strength below specification.

Bench work: use a vice with soft jaws for finished surfaces, support long work with a stand, and mark with a scriber and layout dye before cutting.

Waste segregation: used oil, oil filters, batteries, brake fluid, coolant, tyres and metal swarf are separate streams; mixing them makes the whole batch hazardous waste.

Used engine oil is a controlled waste; store in labelled, lidded containers and send to a licensed collector, never to drains or soil.

Lead-acid batteries contain lead and sulphuric acid; return to a licensed recycler, and never store them where acid can leak into groundwater.

Coolant (ethylene glycol) is toxic and sweet-tasting; keep it away from animals and children and dispose of it as hazardous waste.

Refrigerant and aerosol cans must not be punctured or burned; recover refrigerant with approved equipment.

Spill response: absorb with a spill kit or sand, contain the spread, clean the area, and report according to the site procedure.

Energy and noise: switch off compressors and lights when not in use, and use hearing protection where noise exceeds about 85 dB(A).

Symptom-to-system map: no crank = battery/starter circuit; crank but no start = fuel, spark or compression; starts then dies = fuel supply or idle circuit.

Overheating causes: low coolant, faulty thermostat, blocked radiator fins, lean mixture, retarded ignition or a slipping clutch under load.

Blue smoke = oil burning (rings, valve guides, turbo seals); black smoke = rich mixture; white smoke = coolant entering combustion (head gasket).

Vibration and noise: loose engine mounts, worn swingarm bearings, unbalanced wheels, worn chain and sprockets or a failing bearing.

Brake drag: check caliper piston seizure, contaminated fluid, a bent disc or a misadjusted master cylinder pushrod.

Electrical intermittent faults: inspect earth points, connector corrosion and harness chafing; a voltage drop test across a connection locates high resistance.

Fuel smell and poor economy: leaking injector, stuck choke/enricher, dirty air filter or a faulty coolant temperature sensor making the ECU enrich the mixture.

Before any repair, record baseline measurements (compression, voltages, clearances) so the effect of the repair can be verified.

Job card must record the complaint, the diagnosis, the parts used (with part numbers), the labour time and the technician's signature.

Use the manufacturer's service manual for torque values, clearances and fluid specifications; generic data can be wrong for a specific model.

Warranty work requires the fault to be documented with measurements and photographs where the manufacturer specifies.

Before handing over, explain the work done, any remaining faults and the next service interval to the customer, and record the advice.

Parts identification: use the VIN and engine number to confirm the correct variant, because the same model year can have different components.

Safety-related defects (brakes, steering, tyres, fuel leaks) must be reported and corrected before the machine is released.

Two-stroke: one power stroke per revolution, ports instead of valves, crankcase induction; higher power per litre but poorer emissions and narrower power band.

Two-stroke lubrication is by oil mixed with fuel or by an oil pump; a failed pump or a forgotten premix causes rapid seizure.

Four-stroke: valves, camshaft and timing chain/belt; valve timing and clearance directly affect breathing and compression.

Two-stroke exhaust expansion chamber uses pressure waves to supercharge the cylinder and reduce fresh charge loss; a dented chamber changes the power curve.

Scavenging in a two-stroke relies on transfer ports; worn piston/rings reduce crankcase sealing and cause hard starting and poor idle.

Four-stroke valve seat recession and burned valves follow from too little clearance; check clearance at the specified interval and set cold.

5S: sort, set in order, shine, standardise, sustain; a clean bench reduces lost tools and cross-contamination of parts.

Tool shadow boards and labelled storage make missing tools visible immediately, which prevents foreign objects entering engines.

Cleanliness rule: cap or plug open ports, fuel lines and brake lines during repair; a single stray washer can destroy a gearbox.

Lifting equipment and stands must be rated for the load; never work under a machine supported only by a jack.

Lockout/tagout applies to mains-powered equipment and to battery isolation before electrical work.

Waste bins at the point of use encourage segregation; a mixed bin is a compliance failure, not just a housekeeping issue.

Length: 1 inch = 25.4 mm; 1 mm = 0.03937 in; 1 thou = 0.001 in = 0.0254 mm.

Pressure: 1 bar = 100 kPa = 14.5 psi; 1 atm = 1.013 bar; tyre pressures are often quoted in both bar and psi.

Torque: 1 N·m = 0.102 kgf·m = 0.738 lbf·ft; 1 kgf·m = 9.81 N·m.

Power: 1 kW = 1.341 hp; 1 hp = 0.746 kW; engine power is measured at the crankshaft or rear wheel, and the two differ.

Volume: 1 litre = 1000 cm³; engine capacity in cc equals swept volume in cm³.

Speed and gearing: road speed = (engine rpm × 60 × wheel circumference) / (overall gear ratio × 1000) with circumference in metres.

Inspection stages: incoming (parts), in-process (during repair) and final (before release); each stage has its own check sheet.

Critical dimensions are checked with the correct instrument and recorded; a measurement without a record cannot be audited.

Go/no-go gauges give a fast pass/fail for production checks; they do not give a measured value.

Sampling inspection accepts a batch on a sample; a single critical safety part should be 100 % inspected.

Calibration: measuring instruments must be checked against a standard at defined intervals, and an out-of-calibration instrument invalidates its readings.

Final road test and function check of brakes, lights, steering and leaks is the last quality gate before handover.

Specific gravity of a fully charged lead-acid cell is about 1.265-1.280; 1.120 or below indicates a discharged cell.

Charge rate rule: charge at about one-tenth of the ampere-hour capacity (C/10) for a normal charge; fast charging shortens battery life.

Never charge a frozen battery; allow it to thaw first, and never allow a spark near a gassing battery.

Battery load test: apply the specified load for the specified time and check that voltage stays above the minimum; a battery that fails must be replaced.

Parasitic drain is measured with a multimeter in series with the negative terminal; a reading above specification indicates a faulty circuit or accessory.

Terminal cleaning: remove corrosion with a bicarbonate solution, rinse, dry and apply protective grease; tighten terminals to the specified torque.

Clutch slip under acceleration = worn friction plates, weak springs or incorrect oil; clutch drag = warped plates, air in the hydraulic release or too much lever free play.

Gearbox jumps out of gear = worn dogs, bent shift fork or worn detent; a whine in one gear only points to a damaged gear pair.

Chain and sprocket wear: hooked teeth, a chain that can be lifted more than about half a tooth from the rear sprocket, or tight links mean replacement as a set.

Shaft drive: check bevel box oil level and look for leaks at the pinion seal; a whine that changes with throttle indicates backlash or bearing wear.

Belt drive: check tension at the specified point with the specified force, and check alignment; a stone embedded in the belt damages it.

Hydraulic clutch: a spongy lever means air; bleed with the correct fluid and check the slave cylinder seal for leaks.

Static sag = (free length − loaded length); rider sag is measured with the rider aboard; both must fall within the manual's range before damping is adjusted.

Rebound damping too fast causes a pogo effect; too slow packs the suspension down over repeated bumps.

Compression damping too hard makes the ride harsh and reduces tyre contact; too soft causes bottoming and wallowing.

Fork oil viscosity and level affect damping; a higher level reduces the air volume and increases progressive resistance to bottoming.

Wheel removal: support the machine, loosen the axle before lifting, note the spacer order and the direction arrow on the tyre, and torque the axle on refit.

Tyre fitting: lubricate the bead, seat it evenly, check the rotation arrow and balance after fitting; never exceed the maximum seating pressure.

Voltage drop test: measure across a connection or cable while the circuit is loaded; more than about 0.5 V for a main cable indicates high resistance.

Continuity test is done with the circuit dead; a reading of near zero ohms means a good connection, and open circuit reads infinite.

Current measurement requires the meter in series or a clamp meter; never connect an ammeter across a voltage source.

Resistance measurement requires the component isolated; a reading outside specification indicates an open or shorted coil.

Charging check: measure battery voltage at idle and at about 3000 rpm; it should rise to the regulated range (about 13.5-14.5 V).

Starter current draw: a high draw with slow cranking indicates a seized bearing or a shorted armature; a low draw with no cranking indicates an open circuit.

Fuel filter replacement interval is set by the manufacturer; a restricted filter causes low pressure, lean running and hard starting.

Injector cleaning: a blocked injector causes a misfire on one cylinder; flow test and ultrasonic cleaning restore the spray pattern.

Throttle body and idle air control passages must be clean for a stable idle; carbon build-up causes a hunting idle and stalling.

Evaporative emission system: a charcoal canister traps fuel vapour; a saturated canister or a leaking purge valve causes a fuel smell.

Catalytic converter damage follows from unburned fuel (misfire) or oil burning; a glowing converter or a P0420-type code indicates efficiency loss.

Lambda sensor: a slow or lazy sensor causes poor economy and emissions; check the heater circuit and the signal before replacement.

Cylinder head removal sequence: loosen in reverse of the tightening sequence, and check the head for warpage with a straight edge and feeler gauge.

Valve grinding: check the valve stem for bend, the seat width and the margin; lap the valve and check the contact pattern before assembly.

Piston ring fitting: the ring gaps are staggered (about 120° apart) and the top ring faces up; the ring compressor prevents breakage on insertion.

Crankshaft and connecting rod bearing clearance is checked with Plastigauge; the crankshaft journal is measured for taper and out-of-round.

Cam chain tensioner: a noisy chain or a rattle at start-up indicates a worn tensioner or stretched chain; align the timing marks before assembly.

Oil pressure check with a gauge confirms the pump and bearing condition; low pressure with correct oil level indicates worn bearings or a faulty relief valve.

Brake bleeding sequence: start at the caliper farthest from the master cylinder and work closer; keep the reservoir topped up to avoid drawing air.

Caliper piston removal uses low-pressure air or hydraulic pressure; never use high-pressure air, because the piston can fly out.

Pad and disc cleaning: use brake cleaner, not oil-based solvents; any oil on the friction material means replacement.

ABS system: do not let air enter the modulator; follow the manufacturer's bleed procedure, which may need a diagnostic tool to cycle the pump.

Brake hose inspection: cracks, bulges or a spongy lever indicate internal hose failure; replace hoses in pairs where specified.

Parking brake adjustment follows the shoe or cable specification; a dragging brake overheats the disc and can cause a fire.

Frame alignment check: measure the steering head to swingarm pivot distance and the wheel centre lines; a bent frame must be replaced, not straightened, unless the manufacturer permits it.

Steering head bearing replacement: press the races square, pack with grease and set the preload so the bars fall slowly to one side without play.

Fork tube inspection: check for pitting and bend with a straight edge or V-blocks and a dial gauge; a bent tube must be replaced.

Swingarm pivot bearing play causes rear-end instability; check with the rear wheel off the ground and the shock disconnected.

Subframe and footpeg mounts are crash-damage points; check for cracks at welds and for elongated bolt holes.

Handlebar and lever alignment: controls must be reachable without releasing the grip, and the throttle must snap closed from full lock in both directions.

Coolant type must match the manufacturer's specification; mixing silicate and OAT coolants can cause gel formation and block the radiator.

Pressure test the cooling system to locate leaks; a cap that fails to hold pressure lowers the boiling point and causes overheating.

Thermostat test: suspend it in water and heat; it should begin to open at the marked temperature and be fully open about 10 °C above.

Water pump seal failure shows as a weep from the drain hole; a noisy bearing indicates replacement.

Air bleeding after refill: run the engine with the radiator cap off until the thermostat opens and the level stabilises.

Radiator fin cleaning: use low-pressure water or compressed air from the back; bent fins reduce airflow and cooling.

Oil filter replacement: smear the seal with clean oil, tighten by hand or to the specified torque, and check for leaks after start-up.

Oil level check: machine upright on level ground, engine off and warm, after the specified wait; overfilling causes foaming and seal leaks.

Oil pressure warning light at idle with correct level indicates a worn pump, a stuck relief valve or a blocked gallery.

Oil change interval is shortened for dusty conditions, short trips and heavy load; the filter is changed with the oil.

Oil contamination: milky oil indicates coolant or water ingress; metal particles indicate bearing or gear wear and require investigation.

Two-stroke oil pump adjustment: the pump cable is set so the mark aligns at the specified throttle opening; too little oil causes seizure.

Regulator/rectifier converts AC from the stator to DC and limits voltage; a failed unit overcharges (boiling the battery) or undercharges (flat battery).

Stator test: measure resistance between phases and to earth; an open phase or a short to earth means replacement.

Lighting circuit: check the bulb, fuse, switch and earth; a dim light often indicates a bad earth rather than a bad bulb.

Horn and indicators: a failed flasher relay causes no indicators or a fast flash; LED indicators may need a load resistor or an LED-compatible relay.

Ignition switch and immobiliser: a key not recognised prevents cranking; check the antenna ring and the key battery where fitted.

Wiring repair: solder and heat-shrink a joint, and match the wire gauge; a crimp connector must be the correct size for the wire.

Risk assessment before a job: identify the hazards (fuel, heat, electricity, lifting), decide the controls and record them for significant risks.

Permit-to-work and isolation apply to high-energy tasks; verify isolation by test, not by assumption.

Incident reporting: near misses are reported as well as injuries, because they reveal the same underlying causes.

Housekeeping and PPE compliance are line responsibilities; supervisors must correct unsafe acts immediately.

Training and competence: only a competent person may test-ride, operate a grinder or work on high-voltage (EV) systems.

Environmental duty: report spills, manage waste and use the correct PPE for chemicals, including gloves and eye protection.