LUBRICATION
Lightweight Models
This is by true dry sump system. The oil tank, or reservoir, is integral
with the crankcase. The oil pump has only one moving part, i.e., the oil
pump plunger, which rotates and reciprocates. Rotation is created by the
worm gear on the timing side flywheel axle.
Reciprocation is caused by engagement of the oil pump guide pin with
the profiled groove in the oil pump plunger. The oil pump is designed
so that the sump scavenging capacity is greater than the delivery, thus
keeping the crankcase sump free of oil during normal running conditions.
Whilst the oil reservoir is integral with the crankcase, oil is fed to the
pump by gravity, on the same principle as a machine fitted with a separate
oil tank, but without the use of external oil pipes.
Engine oil pump. If, for any reason, the crankcase is dismantled the oil
pump plunger must be removed from its housing before attempting to
separate the crankcase halves. It is also necessary to remove the small
timing pinion.
Important. Under no circumstances must either the pump plunger or
guide screw be disturbed in ordinary routine maintenance.
Engine oil circulation. Provision is made to observe the oil circulating,
which is visible after removing the oil filler cap on the right side of the
crankcase.
The oil pump forces oil through:—
(a) Passages drilled through the timing side flywheel axle, timing side
flywheel and crank pin to lubricate the timing side bearing and the
big-end bearing. The splash passes to interior of cylinder, to lubricate
the cylinder and piston, and then falls into the crankcase sump.
(b) From the front oil pump housing to the rocker box via passages in
the cylinder barrel, lubricating the rocker gear and valve stems. Oil
from the rocker gear drains by gravity via the push rod tunnels to
the timing gear case at a pre-determined level. The over-spill drains
into the crankcase sump.
(c) The oil pump extracts oil from the crankcase sump, metal impurities
are collected by a magnetic filter incorporated in the sump drain
plug. The oil is again filtered by a fabric filter located in the crank-
case, (see Fig. 3) before returning to the oil tank reservoir.
For valve guide lubrication see paragraph "Adjustment of oil feed".
The oil reservoir. The normal oil level is 1 inch below the filler cap orifice,
the oil content is 2½ pints. Run the engine for a short period to scavenge
the sump, before “topping up”.
After the first 500 miles (800 kilometres) again at 1,000 miles (l600
kilometres) and subsequently at 5,000 mile intervals (8000 kilometres) the
oil reservoir should be drained the oil filter cleaned in petrol and the
reservoir replenished with new oil. It is preferable to drain the oil after
a run and when the oil is warm. A drain plug is fitted to both the crank-
case sump also the oil reservoir. The drain plug for the reservoir is close
to the bottom front crankcase bolt.
The crankcase fabric filter. The filter is cylindrical in shape and made
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