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52
502 50 18-01
Crankshaft and crankcase
The task of the crankshaft is to transform the reciprocating motion of the piston to rotation. This requires a stable design
withstanding immense pressure and rotational and bending strain, as well as high rotational speed. In addition the con-
necting rod is exposed to large acceleration and retardation forces as it moves between the top and bottom dead centres.
This puts special demands on the bearings that must withstand quick changes in load. Moreover, the bearing’s roller
retainer must also cope with high temperatures and friction. It is therefore extremely important when servicing to check
the roller retainer for cracks, wear and discolouration caused by overheating.
The crankshaft is journalled in the crankcase on heavy-duty ball bearings. In addition to the journalling point for the
crankshaft, the crankcase acts as a scavenging pump for the fuel/air mixture when this is “sucked” from the carburettor
and is forced into the cylinder’s combustion chamber. The crankcase must be perfectly sealed so as not to affect this
pump function. There cannot be any leakage from the crankshaft, between the crankcase halves or between the crank-
case and the cylinder.
Always replace the sealing rings and gaskets when servicing the crankcase.
Dismantling
Dismantle all components so that only the
crankcase and crankshaft remain.
Dismantle the guard under the crankcase.
Dismantling
Dismantle all components so that only the
crankcase and crankshaft remain.
See the respective sections for detailed
information if necessary.
Remove the 2 bolts and lift off the guard
from under the crankcase.
Prise off the cable duct and the short-
circuit cable.
Remove the cable duct by using for in-
stance a screwdriver to press on the three
plungers and the grommet for the short-
circuit cable.
Remove the 5 screws holding both crank-
case halves together.
Remove the 5 screws holding both crank-
case halves together.
Содержание 345FR
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