Derbi boulevard 125 4t, Workshop Manual, Page: 127 / 182

- 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.
N.B.
THE HEAD LUBRICATION CHANNEL IS PRO-
VIDED 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
CLOGGING IMPAIRS THE HEAD LUBRICA-
TION AND THE TIMING MECHANISMS. A JET
FAILURE CAUSES A DECREASE OF THE MAIN
BUSHING AND CONNECTING ROD LUBRICA-
TION PRESSURE.
- Inspect the mating surfaces on the crankcase
halves for scratches or deformation, taking partic-
ular with the surfaces that mate with the cylinder
and the mating surfaces between the crankcase
halves.
- Defects in the crankcase coupling gasket or the
surfaces indicated in the figure can cause a drop
in the oil pressure and affect the lubricating pres-
sure for the main bushings and the connecting 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.
Engine
ENG - 127