3
POWERHEAD
3-1
INTRODUCTION
The carburetion
and ignition
principles
of two-cycle
engine operation
MUST
be un-
derstood
in order to perform
a proper tune-
up on an outboard
motor.
Therefore,
it
would be well worth
the time
to study the
principles
of two-cycle
engines
as outlined
in this section.
A Polaroid,
or
equivalent
instant-type
camera,
is an extremely
useful item provid-
ing the
means
of accurately
recording
the
arrangement
of parts
and wire
connections
BEFORE
the disassembly
work begins.
Such
a record is most valuable
during the assemb-
ly work.
Tags
are
handy
to identify
wires
after
they are disconnected
to ensure they will be
connected
to the same terminal
from which
they were removed.
These tags may also be
used for parts
where marks or other
means
of identification
are not possible.
THEORY OF OPERA nON
The two-cycle
engine
differs
in several
ways from a conventional
four-cycle
(auto-
mobile) engine.
1-
The
method
by which
the
fuel-air
mixture
is delivered
to the
combustion
chamber.
2-
The complete
lubrication
system.
3- In most cases, the ignition system.
4-
The frequency
of the power stroke.
These differences
will be discussed
briefly
and compared
with four-cycle
engine opera-
tion.
Intake/Exhaust
Two-cycle
engines
utilize
an
arrange-
ment of port
openings
to admit
fuel to the
combustion
chamber
and to purge
the
ex-
haust
gases
after
burning
has
been
com-
pleted.
The ports
are located
in a precise
pattern
in order
for
them
to be open
and
closed off at an exact
moment
by the piston
as it moves
up and down in the
cylinder.
The exhaust
port
is located
slightly
higher
than the fuel intake
port.
This arrangement
opens the
exhaust
port
first,
as the
piston
starts
downward, and therefore,
the exhaust
phase
begins
a fraction
of a second
before
the intake phase.
Actually,
the
intake
and exhaust
ports
are
spaced
so closely
together
that
both
open almost
simultaneously.
For this
rea-
son, the pistons
of most
two-cycle
engines
have
a deflector-type
top.
This design
of
the
piston
top
serves
two
purposes
very
effectively.
DEFLECTOR
EXHAUST
PORT
EXHAUST
Drawing
to depict
the intake
and exhaust cycles
of a
two-cycle
engine.
Содержание 4906B 4HP 1969
Страница 5: ......
Страница 85: ...3 44 POWERHEAD EXHAUST COVER I LEVER Exploded drawing of a 5 5 hp powerhead 1956 60 principle parts identified...
Страница 87: ...3 46 POWERHEAD Exploded drawing of a 7 5 hp powerhead 1956 58 with principle parts identified...
Страница 88: ...CYLINDER BLOCK 3 47 HEAD GASKET RING...
Страница 89: ...3 48 POWERHEAD HEAD BYPASS COVER Exploded drawing of a 10 hp powerhead 1956 63 with principle parts identified...
Страница 90: ...CYLINDER BLOCK 3 49 THERMOSTAT EXHAUST COVER The...
Страница 137: ...4 46 FUEL LEVER AND LOW SPEED...
Страница 153: ...4 62 FUEL Exploded view of a pressure tyoe fuel tank with major parts identified...
Страница 157: ...4 66 fUEL...
Страница 177: ...5 18 IGNITION FLYWHEEL Exploded drawing of a typical magneto system Only one coil and set of points is shown...
Страница 271: ...8 12 LOWER UNIT PROPELLER Exploded drawing of the Weedless lower unit gear case with major parts identified...
Страница 285: ...8 26 LOWER UNIT Exploded drawing of a lower unit with a window for access to the shift connector...
Страница 412: ...A 16 APPENDIX Wire Identification 33 hp with Generator 1965 67...
Страница 413: ...APPENDIX A 17 o C...
Страница 414: ...Wire Identification 33 hp with Generator 1969 70...
Страница 415: ...APPENDIX A 19 Wire Identification 35 hp 1957 59...
Страница 416: ...A 20 APPENDIX Wire Identification 40 hp Standard Shift with Generator 1960 66...
Страница 417: ...APPENDIX A 21 UJ cc b Wire Identification 40 hp Standard Shift with Generator 1967 68...
Страница 418: ...A 22 APPENDIX ee I U Vl Z Z o U I I Wire Identification 40 hp Standard Shift With Generator 1969 10...
Страница 419: ...APPENDIX Wire Identification 40 hp Electric Shift with Generator 1961 66 A 23...
Страница 420: ...A 24 APPENDIX C 00 Wire Identification 40 hp Electric Shift with Generator 1967 68...
Страница 421: ...Wire Identification 40 hp Electric Shift with Generator 1969 70...
Страница 422: ...NOTES NUMBERS...