PIAGGIO MP3 500 i.e. SPORT Service Station Manual page 229

MP3 500 i.e. SPORT Business_LT_ ABS-ASR_EU_USA (2015)
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 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 obstructions in the oil feeding channels, the matching surface of the two half-bearings must
be perfectly perpendicular 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.
N.B.
TO KEEP THE BUSHINGS ON THE CRANKCASE IN SUCH POSITION, DRIVING IS FORCED ON
CAST-IRON RINGS INSERTED IN THE CASTING OF BOTH CRANKCASE HALVES.
- Check the inside diameter of the main bushings
in the three directions indicated in the diagram.
- Repeat the measurements for the other half of
the bushing. See figure.
N.B.
DO NOT TAKE THE MEASUREMENT ON THE 2 HALF-
SHELLS COUPLING SURFACE SINCE THE ENDS ARE RE-
LIEVED TO ALLOW BENDING DURING THE DRIVING
OPERATION.
Before assembling, check that the clearance between the engine crankcase bushing and the crankshaft
is within the predetermined limits.
Characteristic
Crankshaft-bushing maximum clearance allowed:
0.08 mm
- The standard bushing diameter after driving is variable on the basis of a coupling selection.
- The crankcase bushing seats are classified into 3 categories while the crankshaft ones, into 2 cate-
gories.
- Bushings are subdivided into 4 categories according to their thickness (see the table).
Engine
ENG - 229