Craftsman Motorcycle Vehicles Maintenance flashcards

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

Stoichiometric air-fuel ratio

The mass ratio of air to gasoline that burns completely with no excess oxygen or fuel, approximately 14.7:1 for pump gasoline. Closed-loop fuel injection targets this ratio at lambda 1.0 under light load.

Leak-down test

A diagnostic that pressurizes a cylinder at top dead center and measures the percentage of air escaping. Leakage above 20 percent indicates worn rings, burned valves, or a failed head gasket.

Wet clutch free play

The slack measured at the clutch lever before the cable or hydraulic system begins to disengage the clutch, typically 10 to 20 millimeters. Too little free play causes slip; too much causes drag and hard shifting.

Chain slack measurement

The vertical movement of the drive chain at the midpoint between the front and rear sprockets, measured with the motorcycle resting on its wheels. Typical specification is 20 to 35 millimeters of total movement.

DOT 4 brake fluid

A glycol-based hydraulic brake fluid with a dry boiling point near 230 degrees Celsius and a wet boiling point near 155 degrees. It absorbs moisture over time and requires periodic flushing.

Spongy brake lever

A lever that feels soft and compresses further than normal under pressure, usually caused by air or moisture in the hydraulic circuit. It requires bleeding before the brake can be trusted.

Fork sag

The amount the suspension compresses from fully extended under the weight of the rider and gear. Street settings typically run 25 to 35 millimeters and are adjusted with preload.

Rebound damping

The hydraulic resistance that controls how quickly the suspension extends after being compressed by a bump. Too little causes pogoing; too much causes packing down over repeated bumps.

Battery state of charge

The percentage of charge estimated from open-circuit voltage after a rest period. Roughly 12.6 volts is full, 12.4 volts is 75 percent, and 12.0 volts is about 25 percent.

Voltage drop test

A measurement taken across a circuit while it carries current, revealing resistance in cables, connectors, or grounds. A drop above 0.5 volts on a 12 volt circuit indicates a fault.

CAN bus termination resistance

The resistance measured between CAN high and CAN low with the network asleep, normally about 60 ohms because two 120 ohm terminators sit in parallel. A reading of 120 ohms means one terminator is missing.

Steering head bearing brinelling

Indentations worn into the bearing races at the straight-ahead position, felt as a notch or detent when sweeping the handlebars lock to lock with the front wheel raised.

JASO MA oil

A motorcycle oil specification for wet clutch compatibility, ensuring friction modifiers are controlled so the clutch engages without slipping. Automotive energy-conserving oils can cause clutch slip.

Valve clearance

The gap between the valve stem and the camshaft lobe or rocker arm, measured with a feeler gauge at the specified engine temperature. Too little clearance can hold a valve open and burn it.

Compression test procedure

A test performed with the engine warm, throttle wide open, and all spark plugs removed, cranking until the gauge peaks. Healthy cylinders typically read 120 to 180 psi with under 10 percent variation.

Fuel pressure drop test

A measurement of how quickly fuel pressure falls after the key is switched off, checking the check valve and injector sealing. A rapid drop points to a leaking injector or failed check valve.

Spark plug heat range

A rating of how quickly a plug dissipates heat from its tip. A hotter plug runs hotter and resists fouling; a colder plug resists pre-ignition in high-load engines.

Three-way catalyst monitor

A diagnostic comparison of upstream and downstream oxygen sensor signals. If the downstream signal mirrors the upstream, the catalyst is no longer storing oxygen and has failed.

Clutch slip test

A check performed by applying strong torque in a tall gear at low road speed. If engine speed rises faster than road speed, the clutch is slipping from worn plates, weak springs, or contaminated oil.

Sprocket wear limit

The point at which sprocket teeth become hooked or pointed, or the chain can be lifted more than half a tooth height off the rear sprocket. Chain and sprockets should then be replaced as a set.

Brake disc minimum thickness

A specification stamped on the disc hub giving the thinnest allowable rotor. Measure with a micrometer at several points and replace the disc if it falls below this value.

ABS wheel speed sensor

A sensor that reads tone ring rotation to report wheel speed to the ABS module. A damaged tone ring or incorrect air gap disables ABS modulation while base braking remains.

Compression damping

The hydraulic resistance that controls how quickly the suspension compresses over a bump. Too stiff causes harshness and deflection; too soft allows bottoming under braking or in dips.

Static wheel balance

Balancing a wheel with a stationary fixture so it has no heavy spot, eliminating hop at low speed. Dynamic imbalance appears as vibration at higher speeds and needs spin balancing.

Charging system voltage test

A check of battery voltage at 2000 to 3000 rpm, which should read about 13.5 to 14.8 volts. Lower readings indicate a weak stator, faulty regulator, or poor connection.

Parasitic draw

Current flowing from the battery with the ignition off, measured with an ammeter in series at the negative terminal. Acceptable draw is typically under 30 milliamps.

Swingarm pivot play

Side-to-side movement felt when rocking the swingarm with the rear wheel raised. Any movement indicates worn pivot bearings or bushings and affects handling stability.

Frame crack inspection

A structural check focused on welds near the steering head, swingarm pivot, and engine mounts. Dye penetrant or magnetic particle testing reveals fine cracks not visible to the eye.

Oil viscosity grade meaning

The first number in a multigrade rating describes cold-flow behavior and the second describes viscosity at operating temperature. A 10W-40 flows like a 10 weight cold and a 40 weight hot.

Fastener torque with lubricant

Applying a specified torque to lubricated threads produces higher clamping force than the same setting on dry threads. Lubricated threads can overstress fasteners, so follow the manual exactly.

Wheel bearing play check

Rocking the tire at twelve and six o'clock while the wheel is raised. Movement that is not matched by fork or swingarm movement indicates a worn wheel bearing.

EVAP purge valve failure

A purge valve stuck open allows fuel vapor to enter the intake continuously, causing rich running and rough idle, especially after refueling. A smoke test locates system leaks.