PIAGGIO 633929(IT), Service Station Manual, Page: 147 / 314

Inspecting the crankcase halves
- Before proceeding to check the crankcase
halves, thoroughly clean all surfaces and oil ducts.
- On the transmission-side crankcase half, take
particular care when handling the oil pump com-
partment and the oil ducts, the by-pass duct, the
main bushings and the cooling jet on the trans-
mission 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.
- 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.
- Inspect the coupling surfaces on the crankcase
halves for scratches or deformation, taking partic-
ular care with the cylinder/crankcase surfaces and
the crankcase halves surfaces.
- Defects in the crankcase coupling gasket be-
tween the crankcase halves or the mating surfaces
shown in the diagram, could cause a drop in the
oil pressure lubricating the main bearings and con-
nection rod.
- Check the main bearing seats that limit axial
clearance in the crankshaft show no signs of wear.
The dimension between these seats is measured
by way of the procedure described previously for
measuring the crankshaft axial clearance and di-
mensions.
N.B.
THE JET IS FED THROUGH THE MAIN BUSH-
INGS. PROPER OPERATION OF THIS COMPO-
NENT IMPROVES THE PISTON TOP COOLING.
CLOGGING HAS EFFECTS THAT ARE DIFFI-
CULT TO DETECT (PISTON TEMPERATURE
INCREASE). FAILURE OR LEAK CAN CONSID-
MP3 125
Engine
ENG - 53