APRILIA SCARABEO 500 2008 Service Station Manual page 216

Engine
The high pressure section includes all components located on the engine crankcase; while the low
pressure section only refers to the thermal group.
The trochoidal pump is fitted to the sump and is controlled via a pair of gears.
To guarantee the integrity of the pump, a pre-filter is fitted.
This a screw-in type pre-filter and its plug serves also as the engine oil drainage plug.
Pump delivery is controlled by means of a piston by-pass calibrated to 4 bar. This is located upline of
the cartridge filter and both are installed on the flywheel cover, so that the seal of the filter is subject to
the system pressure.
The by-pass located upline the cartridge filter improves the operating conditions for the filter, particularly
with cold oil.
The filter is equipped with an anti-drain valve and a pressure relief valve; the latter intervenes when the
filtering element causes a pressure drop exceeding 1 ± 0.2 bar.
These conditions naturally occur only with cold oil and at high running engine or if the filter is dirty.
The filtered oil is used to lubricate the water pump shaft and once at the engine crankcase, to lubricate
the main bearings, the connecting rod head and the piston cooling nozzle, located on the transmission-
side bearing.
The main bearing on the transmission side is fitted with an oil seal and the respective drain line.
The supply line for the timing system comes from the flywheel-side bearing; the supply to the head is
controlled by the specific spray jet in the engine crankcase.
The components of the timing system work with low-pressure oil.
The camshaft bearings are marked directly on the aluminium of the head; the camshaft axial clearance
is partially compensated by the oil supplied to the smaller diameter bearing.
The camshaft supplies the lubricant to the rocking levers via the bores provided; these are installed in
a position so as to ensure that the lubrication is maintained even after the vehicle has stopped. This is
achieved when the camshaft reaches its most usual and likely position when the engine is switched off.
The oil used to lubricate the head returns to the sump via the chain casing channel and therefore it also
provides lubrication for the chain.
In order to avoid that the gas collected from the crankcase carries oil, a one-way valve and a decantation
chamber are used. The one-way valve is a metal reed valve; the decantation chamber has a drainage
hole. A failure in these components implies oil getting into the line supplying air to the engine.
Excessive oil vapours may result in the clogging of ducts on the throttle body.
In order to signal low oil pressure in the system, a pressure switch is used, located immediately after
the oil filter outlet.
The lubrication circuit does not include the countershaft; it is lubricated by the oil transported by the
gearing or by the centrifugal effect of the crankshaft.
The same applies to the piston or the pin, but in this case the cooling nozzle is particularly important.
ENG - 216
SCARABEO 500