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- For the flywheel side half-crankcase, special at-

tention should be given to the lubrication channels

for the main bearings and to the compartment and

the channels for the oil pump, as well as to the duct

for the by-pass located on the flywheel cover.

N.B.

AS ALREADY DESCRIBED IN THE "LUBRICA-

TION" CHAPTER, IT IS ESPECIALLY IMPOR-

TANT THAT THE BY-PASS HOUSING ON THE

FLYWHEEL COVER IS FREE FROM WEAR

THAT MAY IMPAIR THE PROPER SEALING OF

THE LUBRICATION PRESSURE ADJUSTMENT

PISTON. THE HEAD LUBRICATION CHANNEL

IS PROVIDED WITH A SHUTTER JET; THIS

GIVES A "LOW PRESSURE" HEAD LUBRICA-

TION. THIS CHOICE WAS MADE TO REDUCE

THE OIL TEMPERATURE IN THE SUMP.

The jet clogging impairs the head lubrication and the timing mechanisms.

A jet failure causes a decrease of the main bearing and connecting rod lubrication pressure.

- Check that the surfaces are free from dents or deformations, with special attention to the crankcase

coupling and the crankcase-cylinder surfaces.

- Any defects in the crankcase gasket or matching surfaces (see Flywheel cover coupling) can cause

pressurised oil leaks, thereby affecting the connecting rod and main bearing lubrication pressure.

- Check the main bearing seats that limit axial clearance in the crankshaft show no signs of wear. For

the dimensional check, refer to the instructions relating to the axial clearance and dimensions check on

the crankshaft

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.

MP3 400 i.e. Engine

ENG - 87

PIAGGIO MP3 400 i.e. User Manual

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