Crankshaft And Crankcase - Husqvarna 122 HD60 Workshop Manual

7
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 connecting 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 crankcase and the cylinder.
Always replace the sealing rings and gaskets when servicing the crankcase.
44

Crankshaft and crankcase

Dismantling
Dismantle all components so that only the
crankcase and crankshaft remain.
Remove the 3 screws holding both
crankcase halves together.
Separate the crankcase halves.
502 71 27-01
Lift out the crankshaft.
Clean any gasket remains from the
sealing surfaces.
Dismantle the ball-bearings from the
crankcase halves.
Dismantling
Dismantle all components so that only the
crankcase and crankshaft remain.
See the respective sections for detailed
information if necessary.
Remove the 3 screws holding both
crankcase halves together.
Separate the crankcase halves. A special
tool is not required.
Lift the crankshaft out of the crankcase
half on the starter side (a special tool is
not required).
The crankshaft has a snug fi t in the
crankshaft bearing.
Clean any gasket remains from the
sealing surfaces.
Dismantle the ball-bearings from the
crankcase halves.
Heat the crankcase halves to 120°C using
a hot air gun.