Royal Enfield 350 BULLET 1989, Workshop Maintenance Manual

Page: 38 / 114

WORKSHOP MANUAL BULLET
Page 38
LUBRICATION SYSTEM
Lubrication system is by Dry Sump and effected by an automatic and positive double action oil
pumps.
The oil tank is integral with the crankcase, for ensuring the full rate of oil circulation immediately
when the engine is started and for rapid heating of the oil in cold weather. The capacity of the oil sump
is 2.25 Liters. (SAE 50 grade). There are two piston type oil pumps running at 1/12 of engine speed
positively driven by the worm gear on the timing shaft.
The feed pump is at the rear of the timing cover (Left side when viewed from the front) and pumps
oil from the oil tank, through the oil filter to the big end through the timing shaft. After lubrication of
the big end bearings, the oil splashes and lubricates the cylinder barrel walls and drains to the bottom
of the crankcase.
The return pump (front side of the timing cover) draws the oil from the crank case through the
drilled passage and passes through the rocker oil pipe and lubricates the rocker bearings and valve
spring mechanism and flows down though the push rod tunnels into the timing cover chest.
From here, the drained oil is pumped back to the oil tank through a hole (drilled in the RH
crankcase) by the two idler pinions. The return pump has a capacity of approximately double that of
the feed pump, which ensures that oil does not accumulate in the crankcase. If allowed to accumulate
it will lead to smoke - oil splash through breather pipe and starvation of oil to rocker arm bearings.
LUBRICATION SYSTEM
Both pumps are double acting,
but two sides of feed pump are
inter-connected, thereby giving an
augmented and even supply to the
big-end. Return pump is also inter-
connected for effective scavenging
from crank case.
Gauze strainers are provided for
both feed and return filters from the
crankcase to ensure oil is free from
dirt and sludge.
Oil Filter: The oil filter has a
special and important feature in
design. In the case of clogged filter
or should it be neglected the oil
pressure will lift the spring and cap
off of its seat, thereby automatically
by-passing the filter so that the big
end bearings will not be deprived of
lubrication, even though the oil may
be dirty.
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