.
PRESSURE
LUBRICATION
All
engines
use
an
oil
pump
to
provide
a
constant
flow
ofoil to theengine parts.Theoil supply collect sin the
oil base where
it
is picked up by the oil pump pick-up
cup.
A
by-pass valve is
used
to control
oil
pressure.
Drain oil before removing oil base and always use a
new gasket when replacing the oil base.
Oil
Pump
The oil pump (Figure 4) is mounted behind the gear
cover and is driven by the crankshaft gear. Inlet pipe
and screen assembly are attached directly to the
pump body.
A
discharge passage in pump cover
registers with a drilled passage in the crankcase.
Parallel passages distribute oil to the front main
bearing, rear main bearing, and pressure control
bypass valve.
Check oil pump thoroughly for worn parts.
Oil
pump
to prime it before reinstalling. Exceptfor gaskets and
pick-up cup, component parts
of
the pump are not
available individually. Install a new pump assembly
if
any parts are worn.
Oil
By-Pass
Valve
The by-pass valve (located to the right and behind
gear cover), controls oil pressure by allowing excess
oil to flow directly back to the crankcase. Normally
the valve begins to open about
20
psi (138 kPa).
The valve is non-adjustable and normally does not
need maintenance. Determine if valve is operating
normally by inspecting plunger action as follows:
1. Remove the 3/8 x
24
x 7/8 cap screw located
behind gear cover and under governor arm.
2. Remove spring and plunger with a magnet tool.
OIL
PUMP
PICK-UP
CUP
OIL
PUMP
ASSEMBLY
CRANKCASE
TURNED
ON
LEFT
SIDE
Ls-iiog
FIGURE
4.
OIL
PUMP
ASSEMBLY
3. Determine proper valve operation by checking
the spring and plunger according to the following
measurements.
Plunger Diameter.,
........
0.3105 to 0.3125 in.
(7.89 to 7.94 mm)
Spring
Free Length..
...........
1.00
inch (25.4 mm)
when compressed to
0.5
inch (12.7 mm)
Load
............
2.6
f
0.2
Ibs
(11.6
&
0.9 N)
4.
Check the valve seat and clean away any accumu-
lation of metal particles which could cause erratic
valve action. Verify that the valve seat is not
damaged.
5.
Clean plunger and spring in parts cleaning solvent
and install.
Circumferential grooves in the main bearings supply
oil to connecting rod bearings through drilled pas-
sages from each main journal.
A
drilled passage
connects the front main bearing oil supply to the front
ted. Oil overflow from the bypass valve furnishings
lubrication to the camshaft drive gears.
Normal oil pressure should be 30 psi
(207
kPa) or
higher when the engine is at normal operating
temperature. If pressure drops below this value at
governed speed, inspect oil system for faulty
components.
*
camshaft bearing; rear cam bearing is splash lubrica-
.
Redistribution or publication of this document,
by any means, is strictly prohibited.
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