Motorcycle/Small Engine NC II flashcards

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

Carbon monoxide hazard

Colorless, odorless gas in exhaust that binds hemoglobin and can kill in enclosed spaces. Run engines only with forced ventilation and a CO monitor.

Used oil disposal rule

Used engine oil is hazardous waste. Drain into a labeled closed container, never into drains or soil, and release only to an authorized recycler.

Micrometer least count

On a standard metric micrometer the thimble has 50 divisions over 0.5 mm, so each division equals 0.01 mm of measurement resolution.

Vernier caliper reading

Read the main scale at the vernier zero, then add the coinciding vernier line multiplied by the least count, typically 0.02 mm for a 50-division scale.

Plastigauge purpose

A crushable plastic strip placed across a bearing journal. After torquing and disassembly, its flattened width indicates oil clearance against a printed scale.

Valve clearance check

Measure the gap between valve stem and rocker or cam with a feeler gauge at TDC compression, engine cold unless the manual states otherwise.

Chain slack measurement

Free play measured at mid-span between sprockets with the motorcycle unloaded. Adjust to the manual's specification, commonly 20 to 30 mm.

Battery state of charge

Open-circuit voltage indicates charge: about 12.6 to 12.8 V is full, 12.4 V is 75 percent, 12.2 V is 50 percent, and 12.0 V is 25 percent.

Voltage drop test

Measure voltage lost across a circuit under load. More than roughly 0.5 V on a starter cable indicates excessive resistance from corrosion or loose connections.

Leak-down test interpretation

Air escaping from the exhaust indicates a leaking exhaust valve, from the intake an intake valve, and from the oil filler worn piston rings.

Charging system voltage check

With the engine at mid-rpm and lights on, battery voltage should rise to roughly 13.5 to 14.5 V. Outside this range indicates stator or regulator fault.

Compression test with oil

If a low compression reading rises after adding oil to the cylinder, rings are likely worn; if it stays low, suspect valves or head gasket.

Ring end gap check

Square the ring in the cylinder bore using a piston, then measure the gap with a feeler gauge. Too small a gap causes ring breakage when hot.

Cylinder taper

The difference between the largest and smallest bore diameter measured along the cylinder axis. Exceeding the service limit requires reboring or replacement.

Valve seat contact width

The band where valve face meets seat, typically 1 to 1.5 mm. It should be centered on the valve face and verified with marking compound.

Cam timing alignment

At TDC the cam sprocket mark aligns with the head surface and the crankshaft mark with the case mark. Verify before fitting the chain tensioner.

Stoichiometric air-fuel ratio

For gasoline, about 14.7 parts air to 1 part fuel by mass. Richer mixtures add power and cooling; leaner mixtures risk overheating and detonation.

Float level adjustment

The fuel height in the carburetor bowl set to the manual's specification. Too high causes flooding and rich running; too low causes lean surge and hard starting.

Carburetor main jet circuit

Controls fuel delivery at high throttle openings. The pilot circuit handles idle, and the jet needle and needle jet handle mid-range throttle.

Spark plug heat range

A rating of how quickly the plug sheds heat. A hotter plug resists fouling; a colder plug resists pre-ignition in high-load, high-speed engines.

Clutch free play

The slack at the lever or cable before the clutch begins to disengage. Too little causes slipping; too much causes drag and difficult shifting.

Final drive ratio

Driven sprocket tooth count divided by drive sprocket tooth count. A higher ratio increases acceleration and reduces top speed.

Clutch slip symptom

Engine speed rises without matching road speed, especially under load. Causes include worn friction plates, weak springs, or incorrect oil.

Chain and sprocket wear

Replace chain and sprockets together when the chain exceeds its wear length or sprocket teeth hook. Mixing new and worn parts accelerates wear.

Labor cost formula

Labor cost equals labor hours multiplied by the shop labor rate. Use manufacturer flat-rate times where published rather than estimated hours.

Estimate total formula

Estimate total equals parts cost plus labor cost plus applicable taxes and fees. Obtain customer approval before exceeding the written estimate.

Cost variance meaning

Actual cost minus estimated cost. A positive result means over budget and must be explained in the service report with the reason.

Job order contents

Customer details, unit identification, reported complaint, diagnosis, work performed, parts used, labor time, technician name, and date of service.

Informed consent rule

Additional work beyond the approved job requires customer approval first. Record the approval with date, time, and the person who authorized it.

Safety-critical defect reporting

Brakes, steering, tires, and fuel leaks must be reported to the customer even when found outside the requested job, because they affect rider safety.

Customer confidentiality

Customer contact details, vehicle data, and service history are not disclosed to third parties without consent, except as required by law.

Conflict resolution sequence

Listen without interrupting, restate the concern, verify facts against records, present options, and document the resolution agreed with the customer.