General Theory Of Operation; Theory Of Ignition Systems - Westerbeke ATOMIC 4 Operation And Maintenance Manual

commutator and brushes. Do not oil
the commutator.
i. Generator
Oil bearings. Seal moisture tight
to prevent corrosion.
~.
Battery
Remove battery and store in a warm
dry place. Battery sbould be fully
cbarged wben placed in storage and
cbecked periodically. Occasional
cbarging may be desirable to pro-
long battery life. Terminals sbould
be clean and coated witb vaseline
to prevent corrosion.
SECTION IV
THEORY OF OPERATION
1. GENERAL THEORY OF OPERATION
a. UNIVERSAL engines are four cycle,
water cooled, "L" bead and valve-
in-head engines. While various mo-
dels of the engine may ·use differ-
ent fuels and may vary in number
of cylinders, the basic operation
of the engine remains tbe same.
b. While operating, a four cycle
engine goes through four separate
steps to complete one working or
power cycle. These steps are:
intake, compression, power and ex-
haust.
(1) Intake Stroke
As the piston travels down in the
cylinder, tbe intake valve opens.
Vacuum formed on top of the cyl-
inder caused by the downward move-
ment of the piston draws tbe fuel
mixture from tbe carburetor, through
the intake manifold, and into tbe
cylinder compression chamber.
(2) Compression Stroke
As the piston travels up, both
intake and exbaust valves close
and tbe fuel mixture is compressed
between the top of the piston and
the cylinder head.
(3)
Power Stroke
When the piston has reached the
top of its stroke and has just
started down, a properly timed
spark causes tbe fuel mixture to
explode. This explosion drives tbe
-38-
piston down and the power developed
by the sudden tbrust is transmitted
by means of connecting rod and
cranksbaft to the propeller sbaft.
(4)
Exhaust Stroke
The fourth and last stroke occurs
wben the piston again starts its
upward travel. During tbis period
the exhaust valve opens and the
burned gases are forced out of tbe
combustion chamber, into tbe ex-
baust manifold and out tbe exbaust
system.
c. The exbaust stroke marks the end
of one complete operating cycle.
After completion of the exhaust
stroke, the cycle repeats, starting
with the intake stroke and con-
tinues as long as the engine is in
operation.
2. THEORY OF IGNITION SYSTEMS
The Blue Jacket Model AFT and tbe
Utility Models BNM and BNMR are
equipped with a
~agneto
ignition
system. All other models described
in this book have either a
6 or 12
volt, battery operated electrical
ignition system.
a. Battery Operated Electrical
Ignition System
(1) The ignition system consists of
the battery, distributor, ignition
coil, ignition switch, and spark
plugs.