Inspecting The Crankcase Halves - APRILIA SPORTCITY ONE 125 Service Station Manual

Engine
Specific tooling
020074Y Support base for checking crankshaft
alignment
Characteristic
Off-line maximum admitted
A = 0.15 mm
B = 0.01 mm
C = 0.01 mm
D = 0.10 mm

Inspecting the crankcase halves

- Before proceeding to check the crankcase
halves, thoroughly clean the all surfaces and oil
ducts.
- On the transmission side crankcase half, take
particular care cleaning the housing and oil ducts
for the following components: the oil pump, the oil
by-pass valve, the main bushings and the cooling
jet on the transmission side (see diagram).
- Take particular care, also, that there are no signs
wear in the oil by-pass valve housing (see Chapter
Lubrication), as this could prevent a good seal in
the valve, which regulates the oil pressure.
NOTE
THE JET IS FED THROUGH THE MAIN BUSHINGS. PROP-
ER OPERATION OF THIS COMPONENT IMPROVES THE
PISTON TOP COOLING. CLOGGING HAS EFFECTS THAT
ARE DIFFICULT TO DETECT (PISTON TEMPERATURE IN-
CREASE). FAILURE OR LEAK CAN CONSIDERABLY DE-
CREASE THE MAIN BUSHING AND CONNECTING ROD
LUBRICATION PRESSURE.
- On the flywheel side crankcase half, take partic-
ular care cleaning the oil ducts for the main bush-
ings, the oil duct for the jet that lubricates the
cylinder head and the oil drainage duct at the fly-
wheel side oil seal.
NOTE
THE HEAD LUBRICATION CHANNEL IS PROVIDED WITH
A SHUTTER JET; THIS GIVES A "LOW PRESSURE" HEAD
LUBRICATION; THIS CHOICE WAS MADE TO REDUCE
THE OIL TEMPERATURE IN THE SUMP. THE JET CLOG-
GING IMPAIRS THE HEAD LUBRICATION AND THE TIM-
ING MECHANISMS. A JET FAILURE CAUSES A DE-
CREASE OF THE MAIN BUSHING AND CONNECTING ROD
LUBRICATION PRESSURE.
ENG - 106
SPORTCITY ONE 125