Cert III Motorcycle Mech flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Four-stroke cycle order

Intake, compression, power, exhaust. The piston travels four strokes and the crankshaft turns twice for one power stroke, so the camshaft rotates at half crankshaft speed.

Valve clearance measurement point

Measured between cam base circle and follower, with the engine cold unless specified otherwise. On most single-cylinder engines the correct point is top dead centre on the compression stroke.

Compression test conditions

Engine at operating temperature, throttle held wide open, all plugs removed, and cranking until the gauge stops rising. Low or uneven readings indicate ring, valve or head gasket faults.

Torque wrench use rule

Apply the specified figure to the stated thread condition. Lubricated threads reduce friction, so the same torque produces higher clamp load and can stretch or strip fasteners.

Battery isolation sequence

Disconnect the negative terminal first to reduce short-circuit risk, and reconnect it last. This protects tools and the electrical system from accidental contact with the frame.

Petrol flash point

Approximately minus 43 degrees Celsius, meaning petrol gives off ignitable vapour well below normal workshop temperature. No ignition sources near open fuel or drained tanks.

Manual handling limit rule

Use a hoist or two-person lift for engines, frames and other loads above roughly 20 kilograms. Keep loads close to the body and avoid twisting under load.

Hearing protection threshold

Hearing protection is required where noise exposure exceeds 85 decibels averaged over eight hours. Air tools, grinders and running engines without mufflers commonly exceed this.

Safety data sheet purpose

Provides handling, storage, first-aid and disposal information for hazardous workshop substances such as solvents, brake fluid, fuel and used oil. Must be accessible to all workers.

Hygroscopic brake fluid

Brake fluid absorbs moisture from air over time, lowering its boiling point and risking vapour lock under heavy braking. Replacement is typically every one to two years.

Used engine oil hazard

Prolonged skin contact can cause dermatitis and carries a cancer risk. Wear nitrile gloves, avoid solvent washing of hands, and dispose of oil through approved recycling.

Engine operating temperature check

Tests such as compression and clearance checks are performed at the temperature the manufacturer specifies, because metal expansion changes clearances and readings significantly.

Fastener thread condition

Torque specifications assume clean, undamaged threads of the stated type. Dirty or damaged threads give false clamp load, so clean and inspect before assembly.

Chain slack measurement

Measured at the midpoint of the lower chain run with the bike in the specified unladen position. Typical free play is 20 to 35 millimetres depending on model.

Rear wheel alignment check

Alignment is confirmed using swingarm marks or a string line from front to rear wheel. Misalignment causes uneven tyre wear and poor handling, and affects chain and sprocket life.

DOT 4 boiling points

Minimum dry boiling point 230 degrees Celsius and wet boiling point 155 degrees Celsius. Wet figures apply once the fluid has absorbed roughly 3 percent moisture.

Brake disc minimum thickness

Stamped on the disc carrier. A disc worn below that figure must be replaced, since reduced mass lowers heat capacity and can lead to cracking or warp.

Brake disc runout limit

Checked with a dial gauge on the mounted disc, typically limited to about 0.15 to 0.30 millimetres. Excess runout causes pulsation at the lever and uneven pad wear.

Battery state of charge voltages

About 12.6 to 12.8 volts indicates full charge, 12.2 volts roughly half charge, and below 11.8 volts is discharged. Read at rest, 30 minutes after charging.

Charging system voltage test

At around 2000 to 3000 rpm the regulated voltage should sit between roughly 13.5 and 14.8 volts. Higher or lower readings indicate regulator, rectifier or stator faults.

Wheel bearing inspection

With the wheel lifted, spin it and feel for roughness or play at the rim. Any notchiness or axial play beyond specification means bearing replacement, pressed on the inner race.

Suspension setup sequence

Set static and rider sag first, then rebound damping, then compression damping. Damping adjusters are counted in clicks from fully seated clockwise outward.

Tyre pressure cold setting

Pressures are set with tyres cold. A rise above about 10 percent after riding suggests underinflation or overheating, which affects grip, wear and stability.

Tyre date code

Four digits on the sidewall give the week and year of manufacture, for example 2321 means week 23 of 2021. Age and condition guide replacement decisions.

Sprocket wear indicators

Worn sprocket teeth hook or sharpen, and the chain lifts away from the rear sprocket. Chain and sprockets are replaced as a set to avoid rapid new-chain wear.

Clutch cable free play

A small amount of free play at the lever, commonly 2 to 5 millimetres, prevents the clutch slipping when hot and ensures full disengagement when pulled.

Fork oil level setting

Measured from the top of the fork tube with the spring removed and the fork fully compressed. Level changes air-spring volume and therefore bottoming resistance.

Steering head bearing check

With the front wheel off the ground, the steering should fall smoothly to either side without notchiness. Play is checked by rocking the forks with the wheel held.

Multimeter voltage drop test

Measures lost voltage across a connection or cable while current flows. More than about 0.5 volts on a high-current circuit indicates excessive resistance.

Fuse rating rule

A replacement fuse must match the original rating and type. A higher rating allows excessive current and risks cable fire; repeated blowing indicates a short circuit.

Spark plug heat range

The plug's ability to shed heat, chosen to suit the engine. A plug running too hot causes pre-ignition; too cold causes fouling and misfire.

Fuel injection pressure test

Fuel pressure is checked at the specified test port against manufacturer figures, usually several bar. Low pressure causes lean running; high pressure causes rich running.