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Manual
F 240
10. Piston
11. Connecting rod
Ver. 01
PISTON AND CONNECTING ROD
16A
16A
GENERAL DESCRIPTION
GENERAL DESCRIPTION
The piston tightens in the cylinder by means of three compression rings and is
equipped with one oil scraper ring. Dismantling of the piston with connecting rod is only
possible after dismantling the cylinder head.
The steel top part of the piston may not be removed other than in consultation with
the Service Department of Stork--Wärtsilä Diesel. This means that piston heads must
on no account be removed when a routine maintenance job is being effected.
Quick pollution of the pistons may be caused by fuel or lubricating oil of inferior quality,
bad combustion or high lubricating oil consumption.
Stuck piston rings cause loss of power due to escape of air and combustion gases into
the crankcase, which can be detected by excessive crankcase pressure and oil
leaving the sump.
Oil incrustations on the piston should be scraped away carefully, after which the piston
should thoroughly cleaned with gasoil.
Generally it is not necessary to remove the connecting rod from the piston as long as
it moves freely round the gudgeon pin without excessive clearance.
If dismantling of the connecting rod should be necessary remove the locking rings from
the gudgeon pin and push the pin out. It is then possible to remove the connecting rod
from the piston.
Make sure the piston rings move easily in their grooves.
Damaged piston rings should be replaced.
When fitting new piston rings the utmost care must be taken in order not to damage,
deform or break the rings.
When fitting rings care should be taken that they are fitted with the word "Top" to the
top side.
If piston rings that have been used are fitted again, there is the disadvantage that any
unroundness that may have arisen which is difficult to prevent, will only disappear after
a long time by running in.
This may not only be the cause of a high consumption of lubricating oil, but also of
leakage of exhaust gases and pollution of the engine.
Before fitting the new piston rings the grooves in the piston should be oiled. Put the
lock ring for the gudgeon pin back in place and the nuts of the connecting rod bolts
must be tightened with the correct torque and locked in the right way.
When working on the pistons, care should be taken to prevent mechanical damage.
This is particularly important for light metal pistons.
Attention should also be paid that nothing hits the piston when it is hoisted.
Put the piston down by preference on soft material e.g. wood.
Especially the banging of the connecting rod against the piston skirt may cause serious
damage and should always be avoided.
The concerning rod may only be put to rest against the piston skirt very carefully, so
without even the slightest shock.
The connecting rods are open heart steel forgings. The rods are drilled through for the
lubrication oil supply from big end bearing shells to the small end bearing shell.
The small end bearing in the connecting rod is constructed as eye bearing, whilst the
big end bearings are precision bearing shells.
If only the big end bearing shells have to be inspected or replaced, it is not necassary
to remove the piston with connecting rod.
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16 - - 1
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