SECTION C21
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ENGINE LUBRICATION SYSTEM
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The Commando lubrication system is of the dry
sump type, oil contained in the separate oil tank
being fed through a wire strainer by gravity and by
suction through the feed side of the gear type oil
pump to the crankshaft. The oil pump delivers
lubricant under pressure to the oil pressure relief
valve and a bleed off the main feed supplies
lubricant to the rocker gear. The main oil supply
is delivered through the end of the crankshaft,
(which is sealed by a garter type scal in the
timing cover) to both big ends and escapes between
the big end shells and crank journals to lubricate
the cylinder walls, main bearings, camshaft and cam
followers by splash. Oil collects in the crankcase
sump, the inlet rocker box draining through a drill
way in the cylinder barrel, and the exhaust rocker
box draining through a drill way into the push rod
tunnel and providing additional lubrication whilst
returning to the crankcase between the cam
followers to the camshaft.
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The return side of the oil pump draws oil from
the sump via the sump filter (or collecting area in
later crankcases) and returns it to the oil tank. A
bleed from the oil tank return pipe at the tank
lubricates the rear chain via a regulator
comprising a plastic tube and felt insert.
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SECTION C22
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OIL PRESSURE RELIEF VALVE
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The relief valve is fitted to prevent oil
pressure rising above 45/55 Ibs. sq. inch. It is
fitted to the rear of the timing cover below the
rocker oil feed pipe banjo. The valve consists of a
spring loaded steel sleeve pre-set at the factory
using shims to requlate the blow off pressure and
the valve requires no attention. Oil escaping from
the valve returns to the feed side of the pump.
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SECTION C23
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CRANKCASE BREATHER
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A timed and ported mechanical crankcase breather
is usad prior to 1972. In this design, a rotary
disc with cut-away segment driven by the camshaft
and backed with a light spring mates with a similar
stationary disc fitted behind the left camshaft
bush in the crankcase. An elbow with flexible pipe
from the left crankcase leads to the oil tank. The
oil tank breather is connected to the air filter
back plate. 1972 models and later have a
non-mechanical crankcase breather which is located
on the back of the left crankcase and comprises a
microcellular foam insert held in position by
concave washers. The breather pipe is attached to
the top of the breather outlet and the other end to
the top of the oil tank. As with previous models
the oil tank breather is connected to the air
filter back plate.
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SECTION C24
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OIL PUMP
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The oil pump is of the gear type and is shown in
detail in Fig. C29. The return side of the pump,
which is of twice the capacity of the scavenge to
provide sufficient capacity to keep the crankcases
clear of surplus oil, is identified by the wider
gears. The oil pump is sealed to the timing cover
bore with a conical rubber oil seal located on the
pump body by a steel ferrule and compressed by the
timing cover. Removal of the oil pump is included
in Section C16 and the servicing routine covered in
Section C25.
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