Service Sheet No. 1004 (contd.)
Removal of the Connecting Rods and Pistons
With the crankcase and cylinder block upside down on the bench flatten the tab washers
underneath the connecting rod cap bolt nuts and unscrew the nuts. Take off the tab washers and
lift off the big end caps. These are numbered and the caps must be mated with the cor-
responding numbers on the connecting rods. If the bolts are a tight fit in the caps they should be
gently tapped through with the handle of a mallet.
Each connecting rod complete with piston should then be drawn upwards through the
cylinder bore and taken out from the top of the cylinder. Each piston should be immediately
marked on the inside face to show which bore it was taken from and which way it was fitted; a
good plan is to mark the inside of the skirt with the letter "I_" for the left-hand cylinder, putting
the mark on the back of the skirt to denote which way round the piston was fitted. A note should
be made of which way the number on the connecting rod was fitted, or alternatively, mark the web
of the rod in a similar manner to the piston to indicate which cylinder it came from and which way
round it was fitted. Do not in any circumstances mix the big end nuts and bolts; the nuts should be
placed immediately on the bolts from which they were taken to facilitate reassembly. If the wrong
nut is fitted to a bolt it will affect its position and may make it difficult to secure by
the tab washers.
If the unit has covered a considerable mileage there may be a certain amount of sludge built
up in the crankshaft sludge trap, in which case it is advisable for it to be cleaned out.
Procedure is to take out the slotted plug on the drive side end of the crankshaft and the grub
screw in the centre of the crankshaft and then to draw out the sludge trap. (See Fig.
13).
The
passage ways should be cleaned very thoroughly in petrol or by using a suitable degreasing plant.
When reassembling the sludge trap insert the trap into the shaft, then the small centre grub
screw and finally the large screw. . Both the screws must then be centre-punched after final
tightening. This is most important.
With the removal of the
connecting rods and pistons the
crankshaft can be drawn out
from the left-hand side of the.
cylinder block.
The big end bearings should
be bright and free from any
score marks. If there is any sign of
seizure then the bearing shells
should be replaced; in the same
manner the crankpins on the
crankshaft should be c l e a n
a n d b r i g h t . Pi s t o n s should be
carefully examined to see that the
rings are free in their grooves
and that they are not carboned
up or broken. If removed and
gaps checked with .006 in. and
.010 in.
Crankshaft Sludge Trap
Fig. 13.
there is any suspicion that the rings are worn they should be
the ring inside the cylinder bore. The gaps should be between
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