- 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.
Inspecting the crankshaft plain bearings
- To obtain a good bushing lubrication it is neces-
sary to have both an optimal lubricating pressure
(4 bar) and a good oil flow rate; the bushings must
be correctly positioned so as not to obstruct the oil
supply channels.
- The main bushings are comprised of two half-
bearings, one containing holes and channels for
lubrication and the other solid.
- The solid half-bearing is intended to stand the
thrusts caused by combustion, and for this reason
it is arranged opposed the cylinder.
- To prevent shutters in the oil feeding channels,
the matching surface of the two half-bearings must
be perfectly orthogonal to the cylinder axis, as
shown in the figure.
- The oil supply channel section is also affected by
the bushings driving depth compared with the
crankshaft axial clearance of the limiting surface.
NOTE
SPORTCITY ONE 125 Engine
ENG - 107
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