Four-Stroke Engines; Wet-Sump Type; Dry-Sump Type; General - Honda Motorcycle Service Manual

LUBRICATION
FOUR-STROKE ENGINES
Wet-Sump Type
Wet-sump engines contain their total oil volume within their
crankcases. In these systems, oil is pumped from the sump in
the crankcase, through a strainer screen and/or oil filter and
then is pressure fed t o various engine components. Oil return-
ing from these now lubricated areas flows back into the sump
by gravity.
Some wet-sump engines use only a strainer screen t o filter the
oil. Others use a combination of a strainer screen and a
centrifugal-type filter, or a more conventional pleated paper-
type filter.
Dry-Sump Type
Dry-sump systems use an external oil tank and dual-function
oil pumps. In this system, the pump draws in oil for delivery t o
the various components and pumps oil out of the sump and
back to the oil tank.
Since this design eliminates the need for space t o contain the
oil within the lower portion of the crankcases, the engine can
be positioned lower than would otherwise be possible. This
design often incorporates routing and oil storage configura-
tions that aid in lowering oil temperature.
General
A spray-type system is often utilized i n either design illustrated
here as well as in some two-strokes engine designs. Here oil is
literally sprayed through oil jets directly into internal com-
ponents such as the connecting rod, to help ensure lubrication
and cooling of the rods and pistons.
Some systems include oil pressure-controlling relief valves t o
help ensure lubrication even if the filter is clogged or the oil
temperature is so low that it will not flow through the filter.
Oil filters and/or strainer screens are postioned within the
lubrication sytem t o trap contaminants before the oil is routed
back into the lubricant pathways.
OIL TANK
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Date of Issue: Sep..
1988
O
HONDA MOTOR CO., LTD.