Lubrication System; Principle Of Operation; Reasons For Excessive Consumption; Feed Pump - Royal Enfield CO Workshop Maintenance Manual

ROYAL ENFIELD 350cc O.H.V. WORKSHOP MANUAL

LUBRICATION SYSTEM.

23. Principle of Operation.

The lubrication system is of the true dry sump
circulating type. The fact that the oil tank is formed in
the crankcase casting does not affect the principle of
operation, which is identical with that on machines
employing a separate oil tank with connecting pipes.
The oil tank should, therefore, be kept full to
within two inches of the top, as opposed to a car or
lorry engine, in which the level of oil must be kept
well below the crankshaft. The circulation of the oil
is controlled by the feed and return pumps which are
mounted in the timing cover and driven by a cross
shaft and worm gearing from the timing side shaft.
The feed pump is at the rear of the cover and the
return pump at the front. Both pumps are of the
oscillating cylinder type and are double acting, the
space in the pump housing being used to form a
secondary cylinder which gives a delivery stroke
when the main cylinder is on the suction stroke and
vice versa. The operation of these pumps will be
clearly understood on reference to Figs. 23 and 24.
The paths through which the oil circulates are shown

OIL CIRCULATION DIAGRAM

Fig. 25
diagrammatically in Fig. 25. The primary side of the
feed pump B draws oil from the tank A through the
gauze filter C and delivers it through the felt oil cleaner
L to the oil feed nozzle D, pointing down the timing
side shaft, from which it is forced to the big-end
bearing, leakage back into the timing gear being
prevented by a cork oil seal. A release valve at the
inner end of the timing shaft prevents excessive
pressure developing when the oil is cold. This valve is
designed to lift at 30-40 lbs. per sq. in. pressure.
At the same time the secondary side of the feed
pumps draws oil from the tank A through the gauze
filter C and delivers it to the back of the cylinder. The
oil from both the cylinder and the big-end is splashed
round the engine by the flywheels and lubricates the
piston, main bearings and small end, finally collecting
in the two small wells or sumps at the bottom of the
flywheel chamber. From these sumps, both primary
and secondary sides of the return pump F draw oil
through the second gauze filter F and return it to the
tank A through the oil return passage G. The ball
valve in this passage (see Fig. 26) bypasses part of the

BALL VALVE IN OIL RETURN PASSAGE

return oil up the external pipe to the overhead rocker
casing, from which it runs down the push-rod
enclosure tubes and through grooves in the tappet
guides to the timing case which is sealed off from the
flywheel chamber. When the oil reaches a sufficient
level in the timing case the two gear wheels H and J,
which are partially shrouded so as to form a gear
pump, pick it up and return it through the hole K to
the rear portion of the oil tank. Thus, positive
lubrication is provided for the big-end bearing,
cylinder, overhead rockers and timing gear and the
whole of the oil, apart from losses, is collected and
returned to the oil tank.

24. Reasons for Excessive Consumption.

The rate of circulation is approximately 1 gallon
of oil every 20 miles so that to obtain a consumption
figure of 2,000 m.p.g., the amount of oil lost must not
exceed 1% of that circulated through the engine. The
only loss of oil from an engine in good condition
occurs past the piston rings. As cylinder wear occurs
Fig. 26
Page 17