Husqvarna 243RJ Workshop Manual page 54

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.
52
Crankshaft and crankcase
Dismantling
Dismantle all components so that only the
crankcase and crankshaft remain.
Remove the 4 crankcase screws.
Lift off the small crankcase half.
502 71 27-02
Dismantle the ball bearing from the crank-
case half.
Dismantle the crankshaft from the crank-
case half on the fl ywheel side.
504 91 28-00
Dismantling
Dismantle all components so that only the
crankcase and crankshaft remain.
See the respective sections for detailed
information if necessary.
Remove the key for the fl ywheel.
Dismantle the 4 screws holding the crank-
case halves together.
Lift off the small crankcase half and re-
move the gasket.
Use a hot air gun to warm the crankcase
half gently to about 110° C.
Tap the crankcase half against a wooden
block so the ball bearing falls out of its
position.
Use a hot air gun to gently warm the
crankcase half on the fl ywheel side to
about 110° C.
Lift the crankshaft with seated ball bearing
out of the crankcase half.
NOTE!
Place an appropriate mandrel over
the sealing ring so it does not get
damaged during heating.