PISTONS AND CONNECTING RODS—F.2
3.
Check the fitted gap of the compression and
scraper rings. In worn cylinders the gap should be
checked at the bottom of the cylinder. For details
of ring gap dimensions (see Technical Data).
4.
Check the fit of the gudgeon pin in the piston bore
and in the small end bush of the connecting rod.
The pin is a transition fit in the piston, i.e. within the
limits of —0.00015 in (0.004 mm) to +0.00025 in
(0,006 mm). The clearance dimension between
the gudgeon pin and the small end bush of the
connecting rod is between 0.00075 in (0.019 mm)
and 0.0017 in (0,04.3 mm). For details of piston
bore, gudgeon pin and small end bush bore
diameters see Technical Data. To renew the small
end hush, press out the old bush using a suitable
tool. Remove any sharp edges around the small
end parent bore. Press in the new bush, ensuring
that the oil hole in the hush coincides with the hole
in the connecting rod. Ream out the
Fig. F.3.
Exploded view of Piston and Connecting Rod
Assembly.
Fig. F.4.
Numbering of Connecting Rods and Caps.
new hush to suit the gudgeon pin and check the
connecting rod for parallelism (see Technical Data).
5.
Examine the big end bearing shells for wear and
scoring. Also examine the crankpins and if
necessary, remove the crankshaft, regrind the
crankpins and fit undersize bearing shells. These
are available in undersizes of 0.010 in (0.25 mm),
0.020 in (0,51 mm) and 0.030 in (0,76 mm). For
details of crankshaft removal see Page H.31.
6.
If the engine has been in service for a lengthy
period, it is advisable to fit new piston circlips even
if the old ones do not appear to be strained or
damaged.
