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Assam ASSEB Higher Secondary Skill Subject Automotive study materials
Assam ASSEB Higher Secondary Skill Subject Automotive study resources

Assam ASSEB Higher Secondary Skill Subject Automotive practice questions

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Question 1Automotive Workshop Safety, Tools and Equipment

In an automotive workshop, which colour is conventionally used for fire extinguishers and fire-blanket containers so they can be located quickly in an emergency?

  1. Blue
  2. Red Correct answer.
  3. Green
  4. Yellow

Explanation

Fire-fighting equipment is marked in red under common industrial colour-coding practice, so a worker can identify and reach an extinguisher within seconds during a fire. Keeping the red code consistent across the workshop prevents confusion when several types of equipment are mounted on the same wall. Other colours are reserved for different safety meanings such as warning or mandatory actions.

Question 2Automotive Workshop Safety, Tools and Equipment

A technician must raise a vehicle to work underneath it. Which support method is the safe workshop practice?

  1. Stack wooden blocks under the sill wherever it looks strong
  2. Place the vehicle on rated axle stands at the specified jacking points Correct answer.
  3. Lower the vehicle onto bricks placed under the sump
  4. Rest the vehicle on the hydraulic jack alone after lifting

Explanation

A hydraulic jack is a lifting device only and can lose pressure, so the raised vehicle must be transferred onto rigid stands rated for the load. The stands are positioned at the manufacturer's specified jacking points so the body structure carries the weight without deformation. This combination prevents the vehicle from dropping while a person is beneath it.

Question 3Automotive Workshop Safety, Tools and Equipment

Which personal protective item is most important when using a pedestal grinder to sharpen a chisel?

  1. Leather apron
  2. Ear plugs
  3. Impact-rated safety goggles Correct answer.
  4. Cotton gloves

Explanation

Grinding throws high-speed abrasive particles and metal fragments toward the face, so impact-rated eye protection is the primary defence against permanent eye injury. An apron, hearing protection and gloves may be used as secondary protection but do not stop particles entering the eye. Gloves near a rotating wheel also create an entanglement risk.

Question 4Automotive Workshop Safety, Tools and Equipment

What is the correct way to carry a hacksaw across a busy workshop floor?

  1. Hold it above head height so others can see it
  2. Carry it with the blade edge covered and pointing down at your side Correct answer.
  3. Hold it with the blade pointing forward and uncovered
  4. Pass it to the next bench by throwing it underarm

Explanation

A sharp toothed blade should be shielded and directed toward the floor so an accidental contact with a person or bench cannot cause a laceration. Holding it low and to the side also keeps the tool out of the swing path of other workers. This is standard practice for any edged hand tool in a shared workshop.

Question 5Automotive Workshop Safety, Tools and Equipment

Why must the guard on a bench-mounted grinding wheel be adjusted to within about 2 mm of the wheel face?

  1. To reduce the noise produced by the motor
  2. To keep the coolant from splashing
  3. To stop fingers or workpieces being drawn into the gap Correct answer.
  4. To increase the cutting speed of the wheel

Explanation

A small gap between the tool rest or guard and the wheel prevents a workpiece, or a finger, from being pulled into the nip point as the wheel rotates. The gap is checked and adjusted as the wheel wears down. Larger openings defeat the purpose of the guard and are a common cause of serious hand injuries.

Question 6Automotive Workshop Safety, Tools and Equipment

A workshop uses compressed air for cleaning. Which practice is acceptable?

  1. Using a nozzle with reduced pressure and eye protection for bench cleaning Correct answer.
  2. Blowing dust off clothing worn by a colleague
  3. Sealing the nozzle against the palm to test the pressure
  4. Directing the air jet at the skin to cool down

Explanation

Compressed air can force debris or air into the body through the skin, so it must only be used at reduced pressure with eye protection and never aimed at people. Regulated nozzles with safety tips limit the dead-end pressure if the nozzle is blocked. Cleaning the bench, not a person, is the only legitimate use here.

Question 7Automotive Workshop Safety, Tools and Equipment

Which file should be used to remove a large amount of metal quickly from a mild steel bracket before finishing?

  1. A smooth file
  2. A second-cut file
  3. A bastard-cut file Correct answer.
  4. A single-cut file

Explanation

File coarseness is graded by cut, and a bastard cut has deeper teeth that remove material rapidly, making it the choice for roughing down stock. Finer grades such as second-cut and smooth are then used to bring the surface to size and finish. Single-cut refers to the tooth pattern rather than the coarseness needed for fast removal.

Question 8Automotive Workshop Safety, Tools and Equipment

A vehicle on a two-post hoist must be raised for underbody work. What is the correct sequence before anyone goes beneath it?

  1. Raise the vehicle, then shake it to test whether it is stable
  2. Raise the arms, lift the vehicle, and lock the mechanical safety catches Correct answer.
  3. Lift the vehicle to full height and leave it on the hydraulic pressure
  4. Position the arms under the sills and lift without checking balance

Explanation

The lift arms are placed at the manufacturer's lifting points and the vehicle is raised, then the mechanical locks must be engaged so the load is held even if hydraulic pressure is lost. The vehicle should also be checked for balance before anyone works underneath. Relying on hydraulic pressure alone is the classic cause of hoist collapse accidents.

Question 9Automotive Workshop Safety, Tools and Equipment

What is the primary purpose of a torque wrench in engine assembly?

  1. To measure the angle through which a bolt has turned
  2. To tighten a fastener to a specified clamping force without over-stressing it Correct answer.
  3. To check the hardness of the bolt head
  4. To loosen seized bolts with extra leverage

Explanation

A torque wrench signals when the set torque is reached, which controls the clamping force on a joint and prevents bolts from being over-stretched or left loose. Correct clamping is critical for gasketed and rotating joints where uneven torque causes leaks or failure. The tool is a controlled-tightening device, not a breaker bar or hardness tester.

Question 10Automotive Workshop Safety, Tools and Equipment

A socket is marked 12-point. On which fastener is it most appropriate?

  1. A heavily corroded hex nut that is already rounded
  2. A square-headed drain plug
  3. A new hexagonal head bolt in good condition Correct answer.
  4. A splined driveshaft fastener

Explanation

A 12-point socket engages the hex flats at more positions, making it easier to swing in tight spaces, and it works well on undamaged hexagonal fasteners. It contacts less of the flat than a 6-point socket, so it tends to slip on corroded or rounded nuts. Splined and square fasteners need their own matching socket types.

Question 11Automotive Workshop Safety, Tools and Equipment

Why is a micrometer screw gauge zeroed before measuring a valve stem diameter?

  1. To remove any error between the anvil faces so readings are true Correct answer.
  2. To increase the measuring range of the instrument
  3. To warm the instrument to operating temperature
  4. To lock the spindle against rotation

Explanation

Zeroing confirms that the anvil and spindle faces meet cleanly at the zero mark, so any wear, dirt or backlash is compensated before a reading is taken. Without this check, every measurement carries the same constant error. Zeroing does not change the range or the temperature of the tool.

Question 12Automotive Workshop Safety, Tools and Equipment

A hydraulic trolley jack feels spongy and sinks slowly under load. What is the most likely cause?

  1. The jack saddle is made of soft rubber
  2. The handle is the wrong length
  3. The release valve is partly open or the hydraulic fluid is low Correct answer.
  4. The wheels are too small for the floor

Explanation

A spongy feel with slow sinking points to a loss of hydraulic pressure, typically from a partly open release valve, low fluid or an internal seal leak. The jack must be taken out of service and repaired because it can no longer hold a load safely. Wheel size, handle length and saddle material do not affect hydraulic holding ability.

Question 13Automotive Workshop Safety, Tools and Equipment

When jump-starting a vehicle with a flat battery, why is the final negative connection made to a bare metal point on the engine or chassis rather than the flat battery terminal?

  1. It prevents the alternator from charging
  2. It avoids a spark near the battery, which may be releasing hydrogen Correct answer.
  3. It makes the engine crank faster
  4. It reduces the voltage supplied to the starter

Explanation

A lead-acid battery can vent hydrogen, and the last connection is where a spark is most likely; making it away from the battery keeps that spark from igniting gas. The chassis or engine block provides the same return path, so the circuit still works. The order of connection is a fire and explosion precaution, not a performance measure.

Question 14Automotive Workshop Safety, Tools and Equipment

A technician is about to arc-weld a patch onto a vehicle body. Which preparation is essential to protect the vehicle's electronics?

  1. Leave the engine running so the alternator stabilises voltage
  2. Disconnect the battery and unplug sensitive electronic control units, and clamp the earth close to the weld Correct answer.
  3. Connect the earth clamp to the far end of the chassis
  4. Wrap the welding cable around the ECU harness

Explanation

Welding current seeks the path of least resistance back to the earth clamp, and if that path runs through wiring or control units it can destroy them. Disconnecting the battery and unplugging sensitive modules, then clamping the earth close to the work, keeps the current local. This also reduces the risk of fire and electrical damage.

Question 15Automotive Workshop Safety, Tools and Equipment

Which instrument is designed specifically to measure the internal diameter of a cylinder bore?

  1. Vernier caliper with knife edges
  2. Outside micrometer
  3. Feeler gauge
  4. Telescope gauge used with an outside micrometer Correct answer.

Explanation

A telescope gauge is set to the bore diameter and then measured with an outside micrometer, giving an accurate internal reading. A vernier caliper can give a rough inside measurement but lacks the precision and repeatability needed for engine bores. Feeler gauges measure gaps, not diameters.

Question 16Automotive Workshop Safety, Tools and Equipment

What is the correct procedure for safely releasing pressure from a vehicle's fuel system before disconnecting a fuel line?

  1. Disconnect the battery and then pull the line apart quickly
  2. Follow the manufacturer's procedure, such as removing the fuel pump fuse and cranking, then relieve residual pressure at the test port Correct answer.
  3. Crack the line loose while the engine idles
  4. Remove the fuel filler cap and wait one minute

Explanation

Fuel systems stay pressurised after shutdown, so the manufacturer's depressurisation procedure must be followed, for example disabling the pump and cranking the engine, then bleeding residual pressure at the service port. Fuel must be caught in a suitable container and ignition sources removed. Opening a live pressurised line sprays fuel and creates a serious fire hazard.

Question 17Automotive Workshop Safety, Tools and Equipment

A vehicle is to be raised on a single-post or scissor lift in a bay with a low ceiling. What must be confirmed before lifting?

  1. That the bay doors are closed
  2. That the vehicle's fuel tank is full
  3. That the lift's full raised height plus vehicle height fits under the ceiling and the lift locks are functional Correct answer.
  4. That the tyres are inflated to maximum pressure

Explanation

A low ceiling can be struck by the vehicle roof or by the lift structure, damaging both and injuring anyone nearby, so the raised envelope must be checked first. The mechanical locks must also be working so the raised load is held. Fuel level and tyre pressure do not affect the lifting clearance or the safety of the lift.

Question 18Automotive Workshop Safety, Tools and Equipment

Why is a 'dead blow' hammer preferred over a steel hammer when seating a component that must not be marked?

  1. It has a longer handle for more leverage
  2. Its head is filled with shot, which reduces rebound and delivers a controlled blow without sparking Correct answer.
  3. It delivers a harder single blow than steel
  4. It is lighter so it cannot damage the part

Explanation

A dead blow hammer contains loose shot in the head, so the energy is transferred into the work with little bounce, giving control and reducing damage. Its non-sparking face is also safer near flammable vapours. A steel hammer rebounds and can mark or crack the component and may produce sparks.

Question 19Automotive Workshop Safety, Tools and Equipment

A compressed-air line in the workshop has a sudden leak at a quick-release coupling. What is the first safe action?

  1. Isolate the supply at the nearest valve or compressor and release residual pressure Correct answer.
  2. Tighten the coupling by hand while it is under pressure
  3. Hold a rag over the leak and continue working
  4. Spray soapy water on the coupling to locate the leak while it is live

Explanation

The supply must be isolated before anyone works on the coupling, and residual pressure bled off so the fitting can be handled safely. Pressurised air can drive a loose coupling or hose whipping and cause severe injury. Diagnosis and repair are done only after the line is depressurised.

Question 20Automotive Workshop Safety, Tools and Equipment

A four-wheel alignment is being checked and the technician notices the vehicle is on a level, wheel-free lift with the wheels hanging. Why is this incorrect for a thrust-angle reading?

  1. The steering wheel must be locked at full lock
  2. The tyres must be removed for the reading
  3. The wheels must be loaded as if on the ground so suspension geometry is at ride height Correct answer.
  4. The lift must be raised to maximum height

Explanation

Alignment angles are specified at normal ride height with the vehicle's weight on the wheels, so a wheel-free lift changes suspension geometry and gives false readings. The vehicle should be on a level alignment rack or use stands that load the suspension correctly. Ride height and a level surface are the controlling conditions.

Question 21Automotive Workshop Safety, Tools and Equipment

During a cylinder head torque sequence, a bolt is found to be stretched beyond the specified free length. What is the correct action?

  1. Reuse it only on the least stressed position
  2. Reuse it and add extra torque to compensate
  3. Replace the bolt, because a stretched fastener has lost its clamping ability Correct answer.
  4. Shorten the bolt by grinding the end

Explanation

Torque-to-yield and other critical fasteners are designed to stretch within limits; once the free length exceeds specification the bolt has yielded permanently and will not hold the required clamp load. Reusing it risks gasket failure or bolt breakage. The correct action is replacement with the specified new fastener.

Question 22Automotive Workshop Safety, Tools and Equipment

A workshop's air receiver is fitted with a pressure relief valve that has been painted over and is stuck. What is the consequence and the correct response?

  1. The receiver can over-pressurise and burst, so the valve must be freed or replaced and the system tested Correct answer.
  2. No consequence, because the compressor has a cut-out switch
  3. The relief valve only affects air quality, so it can be left
  4. The valve should be removed and the port plugged

Explanation

The relief valve is the last line of defence if the pressure switch or regulator fails, so a stuck valve allows the receiver to over-pressurise to the point of rupture. It must be restored to free operation or replaced, and the system checked by a competent person. A cut-out switch is not a substitute because it can fail too.

Question 23Automotive Workshop Safety, Tools and Equipment

A technician is diagnosing an intermittent electrical fault and proposes to use a test lamp to probe a wire in a harness that feeds an airbag control module. Why is this unsafe?

  1. The lamp will not light on a 12 V circuit
  2. The airbag circuit only works with the engine running
  3. The harness is shielded so probing has no effect
  4. The test lamp draws too much current and can trigger the airbag or damage the module Correct answer.

Explanation

Airbag circuits are pyrotechnic and must be deactivated and given a waiting time before any work; a test lamp injects current and can fire the squib or destroy the control module. A high-impedance digital multimeter and the manufacturer's procedure are used instead. Probing live SRS wiring is a recognised cause of accidental deployment.

Question 24Automotive Workshop Safety, Tools and Equipment

A workshop stores used engine oil, brake fluid and solvent in unmarked containers near a floor drain. What is the main environmental and safety problem and the correct fix?

  1. The containers are too small, so larger drums should be used
  2. Brake fluid can be poured down the drain because it is water-based
  3. Solvent should be left open so it evaporates
  4. Unlabelled mixed waste cannot be legally disposed of and a spill can reach the drain, so each waste stream must be labelled and stored in a bunded area away from drains Correct answer.

Explanation

Waste must be segregated and labelled so each stream can be sent for correct disposal, and bunded storage away from drains prevents a spill entering the watercourse. Mixing wastes makes recycling impossible and can create legal liability and fire risk. Brake fluid and solvent must never be discharged to drains.

Question 25Engine Fundamentals and Construction

In a four-stroke petrol engine, the camshaft rotates at what speed relative to the crankshaft?

  1. One quarter of the crankshaft speed
  2. The same speed as the crankshaft
  3. Half the crankshaft speed Correct answer.
  4. Twice the crankshaft speed

Explanation

Each cylinder fires once every two crankshaft revolutions, so the valves must open and close once per two turns of the crank. The camshaft is therefore driven through a 2:1 reduction and turns at half crankshaft speed. This relationship is set by the timing gears, chain or belt.

Question 26Engine Fundamentals and Construction

The clearance volume of a cylinder is 50 cc and the swept volume is 450 cc. What is the compression ratio?

  1. 10:1 Correct answer.
  2. 9:1
  3. 8:1
  4. 11:1

Explanation

Compression ratio equals total cylinder volume divided by clearance volume. Total volume is swept volume plus clearance volume, that is 450 + 50 = 500 cc. Dividing 500 by 50 gives a compression ratio of 10:1.

Question 27Engine Fundamentals and Construction

Which component converts the reciprocating motion of the piston into rotary motion of the crankshaft?

  1. The flywheel
  2. The connecting rod Correct answer.
  3. The gudgeon pin
  4. The cylinder liner

Explanation

The connecting rod links the piston to the crankpin and swings through an arc as the piston reciprocates. This geometry converts linear piston travel into rotation of the crankshaft. The small end pivots on the gudgeon pin and the big end runs on the crankpin.

Question 28Engine Fundamentals and Construction

In a direct injection diesel engine, where is fuel injected?

  1. Into the exhaust port during valve overlap
  2. Directly into the combustion chamber above the piston Correct answer.
  3. Into a pre-combustion chamber connected by a throat
  4. Into the intake manifold ahead of the inlet valve

Explanation

Direct injection means the injector sprays fuel straight into the combustion chamber, usually into a bowl in the piston crown. The fuel mixes with the swirling compressed air and ignites from the heat of compression. Pre-chamber and manifold injection belong to other diesel and petrol layouts.

Question 29Engine Fundamentals and Construction

Why is a valve clearance specified cold for engines with overhead valves?

  1. To allow for thermal expansion of the valve train when hot Correct answer.
  2. To prevent the valve stem from rotating in its guide
  3. To keep the valve spring preload constant at all speeds
  4. To maintain a fixed camshaft drive ratio

Explanation

Valve stems, pushrods and rockers expand as the engine warms up, so a small gap is set cold to prevent the valve being held off its seat when hot. If the clearance is too small, the valve may not close fully and compression is lost. Too large a clearance causes noise and reduced lift.

Question 30Engine Fundamentals and Construction

Which material is most commonly used for the cylinder block of a modern light automotive engine?

  1. Copper
  2. Cast iron
  3. Aluminium alloy Correct answer.
  4. Mild steel

Explanation

Aluminium alloy blocks reduce weight and give better heat conduction, which is why most modern light vehicle engines use them. Wear resistance is restored with pressed-in or cast-in liners, or by a hard-coated bore surface. Cast iron blocks are still used where strength and cost dominate.

Question 31Engine Fundamentals and Construction

Which type of piston ring is primarily responsible for scraping excess oil from the cylinder wall?

  1. Fire ring of the gasket
  2. Top compression ring
  3. Oil control ring Correct answer.
  4. Second compression ring

Explanation

The oil control ring sits lowest on the piston and has a scraping edge, often with a expander spring, that returns surplus oil to the sump through drain holes. The upper rings seal combustion gases. Correct oil control also limits oil consumption and bore glazing.

Question 32Engine Fundamentals and Construction

What is the main function of the flywheel in an engine?

  1. To store energy and smooth out torque fluctuations between power strokes Correct answer.
  2. To drive the oil pump through a gear train
  3. To filter the engine lubricating oil
  4. To regulate coolant flow through the radiator

Explanation

The flywheel's inertia carries the crankshaft through the non-power strokes and absorbs cyclic speed variation. It also provides a friction surface for the clutch and a ring gear for the starter. A heavier flywheel smooths running but responds more slowly to throttle changes.

Question 33Engine Fundamentals and Construction

A four-cylinder four-stroke engine has a firing order of 1-3-4-2. If cylinder 1 fires at 0 degrees, at what crank angle does cylinder 3 fire?

  1. 360 degrees
  2. 540 degrees
  3. 180 degrees Correct answer.
  4. 90 degrees

Explanation

In a four-cylinder four-stroke engine a power stroke begins every 180 degrees of crankshaft rotation, because 720 degrees is shared among four cylinders. The next cylinder in the firing order therefore fires 180 degrees after the previous one. Cylinder 3 follows cylinder 1 at 180 degrees.

Question 34Engine Fundamentals and Construction

Which type of bearing is normally used for the crankshaft main journals of a passenger car engine?

  1. Taper roller bearing
  2. Plain shell bearing with a thin babbitt or aluminium overlay Correct answer.
  3. Ball bearing
  4. Needle roller bearing

Explanation

Crankshaft main and big end bearings are split plain bearings, usually steel shells lined with a bearing alloy and a thin overlay. They carry high fluctuating loads and rely on a hydrodynamic oil film. Rolling element bearings are not used because the crank is a one-piece shaft and loads are very high.

Question 35Engine Fundamentals and Construction

What is the purpose of valve overlap in an engine camshaft profile?

  1. To keep both valves closed during the compression stroke
  2. To ensure the valves never touch the piston crown
  3. To allow both inlet and exhaust valves to be open briefly around top dead centre Correct answer.
  4. To reduce the lift of the exhaust valve at high speed

Explanation

Overlap is the period when both valves are open near the end of exhaust and start of intake. The outgoing exhaust gas helps draw in fresh charge, improving scavenging and volumetric efficiency. Too much overlap at low speed causes rough idle and poor vacuum.

Question 36Engine Fundamentals and Construction

In a two-stroke engine, what does the term 'scavenging' refer to?

  1. Opening of the reed valve by crankcase vacuum
  2. Mixing of lubricating oil with petrol
  3. Removal of burnt gases by incoming fresh charge Correct answer.
  4. Cooling of the piston by oil spray

Explanation

Scavenging is the process of pushing out residual burnt gas with fresh air-fuel mixture during the transfer phase. In a crankcase-scavenged two-stroke, the descending piston pressurises the crankcase and the transfer ports direct the charge upward. Poor scavenging leaves exhaust gas behind and lowers power.

Question 37Engine Fundamentals and Construction

A mechanic finds that a petrol engine has low compression on one cylinder and bubbles appear in the radiator when the engine runs. Which fault best explains both symptoms?

  1. Worn piston rings only
  2. Blown cylinder head gasket Correct answer.
  3. Clogged air filter
  4. Incorrect ignition timing

Explanation

A failed head gasket can breach the seal between the combustion chamber and a coolant passage. Combustion gas then escapes into the cooling system, producing bubbles, and compression on that cylinder falls. A ring fault would cause low compression but not coolant bubbling.

Question 38Engine Fundamentals and Construction

Which component maintains the correct tension of the timing belt on an overhead camshaft engine?

  1. The tensioner pulley Correct answer.
  2. The crankshaft pulley
  3. The idler pulley
  4. The water pump pulley

Explanation

The tensioner pulley is adjustable and takes up slack in the timing belt so that valve timing stays accurate. Correct tension prevents belt whip, tooth jump and premature wear. An idler pulley only guides the belt and does not adjust tension.

Question 39Engine Fundamentals and Construction

What is the main advantage of a cross-flow cylinder head over a reverse-flow design?

  1. It removes the need for a head gasket
  2. It allows the inlet and exhaust ports to be on opposite sides for better breathing Correct answer.
  3. It makes the engine run without a cooling system
  4. It eliminates the need for a camshaft

Explanation

In a cross-flow head, inlet and exhaust ports open on opposite sides, so incoming charge is not heated by the exhaust side and gas flow is more direct. This improves volumetric efficiency and reduces hot spots. Reverse-flow heads have both manifolds on the same side.

Question 40Engine Fundamentals and Construction

The swept volume of one cylinder is calculated using which formula, where D is bore and L is stroke?

  1. (pi/2) x D x L
  2. pi x D x L
  3. (pi/4) x D x L squared
  4. (pi/4) x D squared x L Correct answer.

Explanation

Swept volume is the volume of the cylinder swept by the piston, equal to the cross-sectional area of the bore multiplied by the stroke. The area is (pi/4) x D squared, so the volume is (pi/4) x D squared x L. Using diameter without squaring gives a linear dimension, not a volume.

Question 41Engine Fundamentals and Construction

Which term describes the distance the piston travels from top dead centre to bottom dead centre?

  1. Clearance volume
  2. Stroke Correct answer.
  3. Bore
  4. Compression height

Explanation

Stroke is the linear distance travelled by the piston between the two dead centre positions. It equals twice the crank radius. Bore is the cylinder diameter, and the two together determine engine displacement.

Question 42Engine Fundamentals and Construction

In an engine with a pressurised cooling system, what is the role of the radiator cap pressure valve?

  1. It opens the thermostat at low temperature
  2. It regulates the engine idle speed
  3. It raises the boiling point of the coolant by holding system pressure Correct answer.
  4. It filters rust particles from the coolant

Explanation

By holding pressure, the radiator cap raises the boiling point of the coolant, allowing a higher operating temperature without boiling. A spring-loaded valve opens at a set pressure to vent to the overflow bottle. A vacuum valve lets coolant return as the system cools.

Question 43Engine Fundamentals and Construction

Which lubrication system is most common on small single-cylinder four-stroke motorcycle engines with a wet sump?

  1. Petroil premix lubrication
  2. Total loss drip lubrication
  3. Pressure feed by a trochoid pump with splash assistance Correct answer.
  4. Grease packed bearings only

Explanation

Most small four-stroke engines use a trochoid or gear pump to feed oil under pressure to the head and bearings, with splash helping cylinder wall and piston pin lubrication. This gives reliable supply at all speeds. Petroil premix belongs to two-stroke engines.

Question 44Engine Fundamentals and Construction

What happens to engine volumetric efficiency if the intake air temperature rises while manifold pressure stays the same?

  1. It increases because hot air flows faster
  2. It decreases because the air charge is less dense Correct answer.
  3. It stays exactly the same
  4. It increases only above 3000 rpm

Explanation

Volumetric efficiency depends on the mass of fresh charge drawn in per cycle. Hotter air has lower density, so a given swept volume holds less mass, reducing volumetric efficiency and power. This is why intercoolers are fitted after turbochargers.

Question 45Engine Fundamentals and Construction

Which of the following best describes the function of the thermostat in an engine cooling system?

  1. It circulates coolant through the engine
  2. It regulates coolant flow to maintain a stable operating temperature Correct answer.
  3. It transfers heat from coolant to the air
  4. It stores coolant for expansion

Explanation

The thermostat is a wax-operated valve that stays closed while the engine warms and opens at a set temperature to admit coolant to the radiator. This keeps the engine within its design temperature band. The water pump circulates coolant, and the radiator rejects heat.

Question 46Engine Fundamentals and Construction

An engine has a bore of 80 mm and a stroke of 90 mm with four cylinders. Using pi = 3.14, what is the approximate total displacement in cubic centimetres?

  1. 1810 cc Correct answer.
  2. 452 cc
  3. 7240 cc
  4. 1440 cc

Explanation

Swept volume per cylinder is (pi/4) x D squared x L. With D = 8 cm and L = 9 cm, area is 0.785 x 64 = 50.24 square cm, and volume is 50.24 x 9 = 452 cc. Four cylinders give about 1808 cc, close to 1810 cc.

Question 47Engine Fundamentals and Construction

What is the primary reason for fitting a counterweighted crankshaft in a single-cylinder engine?

  1. To lubricate the main bearings
  2. To balance reciprocating and rotating masses and reduce vibration Correct answer.
  3. To drive the camshaft at half speed
  4. To increase the compression ratio

Explanation

Counterweights offset the mass of the crankpin, connecting rod and part of the piston, reducing out-of-balance forces and vibration. They also reduce main bearing loads. They do not alter compression ratio or valve timing.

Question 48Engine Fundamentals and Construction

Which component seals the joint between the cylinder block and the cylinder head while also sealing combustion gases, oil and coolant passages?

  1. The valve stem seal
  2. The crankshaft oil seal
  3. The sump gasket
  4. The head gasket Correct answer.

Explanation

The head gasket sits between block and head and must seal three different media at once: high-pressure combustion gas, oil galleries and coolant passages. It is made from multi-layer steel or composite material with fire rings around the bores. Other seals cover different joints.

Question 49Fuel, Lubrication and Cooling Systems

In a four-stroke petrol engine, the component that stores fuel before it is drawn through the fuel line toward the engine is the:

  1. Fuel tank Correct answer.
  2. Carburettor float chamber
  3. Fuel pump
  4. Fuel filter

Explanation

The fuel tank is the bulk storage vessel mounted on the vehicle and holds the reserve of petrol from which the rest of the system is supplied. The float chamber, filter and pump are downstream components that meter, clean or move fuel after it leaves the tank.

Question 50Fuel, Lubrication and Cooling Systems

The main function of the lubricating oil in an engine is to:

  1. Reduce friction and wear between moving surfaces Correct answer.
  2. Increase the octane rating of the fuel
  3. Absorb heat from the combustion chamber walls only
  4. Seal the combustion chamber from the crankcase permanently

Explanation

Oil forms a hydrodynamic film between moving parts such as bearings, pistons and camshafts, separating the surfaces so that friction and metal-to-metal wear are greatly reduced. Cooling, cleaning and sealing are secondary duties that supplement this primary friction-reduction role.