Inspecting The Crankshaft Plain Bearings; Coupling Chart; Refitting The Crankcase Halves - APRILIA SR MAX 125 ie Service Station Manual

Engine
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.

Inspecting the crankshaft plain bearings

crankshaft plain bearings
- To obtain a good bushing lubrication it is neces-
sary to have both an optimal lubricating pressure
(3.2 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 with holes and channels for lubrica-
tion whereas the other is solid.
- The solid half-bearing is intended to stand the
thrusts caused by combustion, and for this reason
it is arranged opposite 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 feeding channel section is also affected by the bushings driving depth compared with the
crankshaft axial clearance of the limiting surface.
NOTE
TO MEASURE WEAR LIMITS AND COUPLING CLEARANCES, SEE THE SPECIFICATIONS CHAP-
TER.
See also

Coupling chart

NOTE
TO MEASURE WEAR LIMITS AND COUPLING CLEARANCES, SEE THE SPECIFICATIONS CHAP-
TER.
See also

Refitting the crankcase halves

crankcase halves
ENG - 146
SR MAX 125 ie