Page H-6
Repair and Service Manual
B
ENGINE
Read all of Section B and this section before attempting any procedure. Pay particular attention to Notices, Cautions, Warnings and Dangers.
Do not sand blast spark plugs. They should be cleaned by
scraping or wire brushing by hand and washing in a commer-
cial solvent.
Spark plugs should be properly gapped to .030" (.76
mm) (CHAMPION RC12YC), given a light coat of anti-
seize compound and tightened to 15 ft. lbs. (20 Nm)
torque.
ENGINE DESCRIPTION
The engine is a four cycle air cooled, V block, twin cylin-
der, overhead valve unit. It incorporates pressure lubri-
cation, and a replaceable oil filter.
The OHV V-Twin engine uses a Magnetron® ignition
consisting of an ignition armature with a self-contained
transistor module. Two armatures are used with a fly-
wheel containing a permanent magnet.
Engine Specifications
Engine model..................................................... 303440
Type.................................... Four cycle, overhead valve
Number of cylinders......................................2 (V block)
Displacement...................................................... 480 cc
Rated horsepower ................................ 16 hp (11.9 kw)
Spark plug type.............................. Champion RC12YC
Spark plug gap........................................ 030" (.76 mm)
Cooling ....................................................................Fan
Oil Filter .......................................Replaceable, Spin-off
Engine Operation
To understand the operation of a four cycle engine, it is
easiest to consider a single cylinder.
The first cycle (stroke) takes place with the piston mov-
ing down and the intake valve open. Fuel is drawn into
the combustion chamber from the carburetor and
through the intake valve and is known as the
intake
stroke.
As the piston reaches the bottom (BDC) of its
travel and starts to move upwards, the second cycle
begins. The intake valve closes which seals the com-
bustion chamber since the exhaust valve is already
closed and causes the fuel air mixture to be compressed
as the piston rises. This is known as the
compression
stroke.
Just before the piston reaches TDC (Top Dead
Center) the spark plug fires which causes a rapid burn-
ing of the air fuel mixture. The temperature rises rapidly
which causes the air fuel mixture to expand. The piston
has been carried through TDC by centrifugal force and
is now forced downwards into the third, or
power stroke
by the expanding gases. As the piston reaches BDC it
enters the fourth cycle. The exhaust valve opens and
the piston rises forcing burned gases from the combus-
tion chamber in what is known as the
exhaust stroke.
As the piston moves through TDC and starts down, the
first cycle is repeated.
The camshaft is gear driven from the crankshaft. The
ignition timing is controlled by an electrical pulse
received from a magnet mounted on the crankshaft fly-
wheel. The ignition timing is not adjustable.
VEHICLE PREPARATION TO TEST
ENGINE CONDITION
Tool List
Qty.
Heat resistant gloves ...................................................1
Pliers ............................................................................1
Compression gauge.....................................................1
Spark plug socket, 5/8” ................................................1
Ratchet ........................................................................1
To prevent possibility of personal injury, dis-
connect negative (-) battery cable before
beginning starter/generator removal.
To properly prepare for a compression test:
a) If possible, drive vehicle long enough to bring the
engine to normal operating temperature.
b) Engage neutral lock per Section B.
c) Disconnect fuel line from fuel tank and plug line to
prevent contamination. Run engine until it stops
from lack of fuel.
d) Remove the air filter to eliminate the possibility of a
restricted air passage.
e) A good, well charged battery should be used.
Weak batteries may not provide the correct crank-
ing speed.
f) Starter belts that drag or slip will affect the com-
pression reading. Adjust belt as necessary.
To prevent possibility of personal injury, never
operate without magneto being grounded. Any
fuel drawn into the cylinders will be expelled
through the spark plug opening and could be
ignited by the ignition system or another
source, resulting in
a
fire.
g) Ground magneto by attaching a wire lead, with alli-
gator clips, from the terminal with the white wire
NOTICE
Summary of Contents for 625619 2012
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