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WorksheetsSmall Engine Midterm Practice
Total questions: 42
Worksheet time: 21mins
The middle piston ring in a 4-stroke engine serves what purpose?
applies oil film
adds friction to slow the engine
acts as a wiper for excess oil
for piston balance
The ___ effect valve rotation.
all answers
valve springs
valve spring retainers
offset cam lobe
The bottom piston ring on a four-cycle engine works to control
oil application to the cylinder
piston slap
excessive compression
piston/cylinder clearance
Which ring prevents the majority of the expanding compression gases from getting past the piston into the crankcase?
o-ring
wiper ring
compression ring
oil control ring
The force applied to the piston is a result of
pressure from the compression stroke
none of the answer choices
gas expansion because of heat
leverage because of the length of the connecting rod
Camshaft timing can be verified externally by using which of these methods?
not possible
valve overlap occurs exactly at TDC between the intake and exhaust stroke
valve overlap occurs exactly 1/2" before TDC on the exhaust stroke
you have to pull the side cover or sump and verify dot to dot
What system is built into some 4-stroke engines to aid in startability by means of less effort from the operator?
primer
choke
compression release
longer rope
Small engine pistons must withstand
mechanical load
all
thermal stress
pressure fluctuations
Engine valve overlap is most useful at ___.
the transition from the carburetor low speed circuit and high speed
higher engine speeds
engine startup
acceleration under heavy loads
Pistons that have a mark in the crown indicate they are directional because they are
forged
elliptical
have an offset wrist pin
used in a vertical shaft engine
The two common cylinder wall types that are used on 4-stroke engines...
aluminum and cast iron
cross hatch and honed
polishing and diamond bore
none of the available answers
Most valve in a small engine rotate around the valve stem axis
true
false
___ cools the exhaust valve.
none
contact with the valve seat
cool air from the flywheel fan
a fuel air mixture that moves into the combustion chamber
____ cools the intake valves.
The fuel and air mixture that moves inside the combustion chamber
cool air from the flywheel fan
contact with the valve seat
sodium in the valve stem
The charge enters the ___ in a gaseous state.
preignition chamber
combustion chamber
valve seat
cooling fin
The amount of thermal expansion is dependent on several factors, including the quantity of material at various locations in a component. Which part of the piston expands the most during normal engine operation?
the piston head
the piston pin bore area
the skirt
the ring lands
When there is too much valve clearance on a four stroke engine, the valves
open too late and close too soon
open too soon and close too late
open too soon
stay open too long
In four-stroke cycle small engines, all piston rings rotate during operation. What causes ring rotation?
vibration
ring land clearance
all
engine condition
A torque wrench should be used
On all fasteners specified in the repair manual
only during engine disassembly
only on bolts, never on screws
only on head bolts and rod caps
Safety glasses/googles should be worn when using
All answers
Aerosol sprays
a bench grinder
a punch or chisel
The Consumer Products Safety Commission safety standard requires that the blade of a rotary lawnmower must stop when the operator leaves the zone within
3 seconds
1 second
5 seconds
2 seconds
A parasitic load is any load applied to an engine that is over and above the frictional load of an engine
true
false
Which statement does not describe a function of the flywheel.
the flywheel helps to prevent over speeding the engine
the flywheel maintains inertia
the flywheel provides a location for magnets used in the ignition system
the flywheel has fins on it for cooling an engine
The compressing of the charge does not aid the air/fuel flow into the combustion chamber.
true
false
The crankshaft of a four-stroke cycle engine turns __o to complete one operating cycle.
180
360
540
720
The pressure on the piston, the size of the piston, and the length of the connecting rod determines the amount of torque produced during the power stroke.
true
false
Why must the charge in the combustion chamber be compressed before ignition?
increases the volume of air
cools the charge to make it more dense
improves vaporization of the air and fuel
all answers
Inertia to keep the engine running is supplied by the
crankshaft
flywheel
combustion
piston
A four-stroke engine gets its name from
the number of valves used in the engine design
the number of piston movements during the combustion cycle
the number of engineers who designed the original engine
the number of cylinders it has
During the combustion stroke, what is the position of the intake valve?
stops the exhaust from going into the carburetor
closes slightly
fully closed
opens slightly
Oil viscosity classification is determined by
the Society of Automotive Engineers
Automotive Service Excellence
the American Petroleum Institute
American Society for Testing Materials
The air/fuel charge enters the combustion in a _____ state.
Vapor
Liquid
Both liquid and vapor
None of the answers
The purpose of a carburetor is
to mix fuel and air
to store fuel
to clean the fuel
to maintain constant velocity
A torque wrench should be used
on all fasteners specified in the repair manual
only during engine disassembly
only on bolts, never on screws
only on head bolts and rod caps
Most 4-stroke engines use chokes, dry bulbs, and wet bulbs primers to enrich the air fuel mixture for easier cold starting
true
false
Vapor lock is best described as
hot oil causing the engine to seize
fuel filling the combustion chamber and stopping the piston
fuel bubbles restricting flow of fuel in the fuel system
steam forming from water in the fuel tank
Technician A says 10% (E10) Ethanol in the gasoline is acceptable to use in modern small engines. Technician B says 15% (E15) Ethanol is acceptable to use in modern small engines. Which is correct?
Technician A is correct
Technician B is correct
Both technicians A and B are correct
Neither technicians A nor B are correct
Gasoline blended for use in the winter is highly volatile compared to fuel blended for use in the summer
true
false
Pilot jets provide _____ for the idle circuit.
better acceleration
fuel
nothing
enhances atomization
Vaporization is the process in which a liquid is sufficiently cooled to change states of matter from a liquid to a vapor.
True
False
Diaphragm carburetors do not have a _____
stenson valve
bunson jet
inlet needle
float
Piston ring rotation hinders engine durability.
True
False
