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2A.12
Air-cooled two-stroke engine
14.16 lnspect the mounting bushes
(A) an
housings (B)
12 Small cracks or holes in aluminium
castings may be repaired with an epoxy resin
adhesive as a temporary measure. Permanent
repairs can only be effected by welding, and
only a specialist in this process is in a position
to advise on the economy or practical aspect
of such a repair. If the right-hand crankcase
half is damaged beyond repair it can be
replaced individually; the left-hand crankcase
half is only available as part of a complete
crankcase assembly.
13 Damaged threads can be economically
reclaimed by using a diamond section wire
insert, of the Heli-Coil type, which is easily
fitted after drilling and re-tapping the affected
thread. Most motorcycle dealers and small
engineering firms offer a service of this kind.
14 Sheared screws can usually be removed
with screw extractors, which consist of a
tapered, left thread screw of very hard steel.
These are inserted into a pre-drilled hole in
the stud, and usually succeed in dislodging
the most stubborn screw. If you are in any
doubt about removing a sheared screw,
consult a Peugeot dealer or a specialist
motorcycle engineer.
15 Always wash the crankcases thoroughly
after any repair work to ensure no dirt or metal
swarf is trapped inside when the engine is
rebuilt.
~d the main bearing
14.18 The crank assembly big-end (A) and main bearings (B)
16 lnspect the engine mounting bushes (see
illustration).
If
they
show
signs
of
deterioration replace all three at the same
time. To remove a bush, first note its position
in the casing. Heat the casing with a hot air
gun, then support the casing and drive the
bush out with a hammer and a suitably sized
socket. Clean the bush housing with steel
wool to remove any corrosion, then reheat the
casing and fit the new bush. Note: Always
support the casing when removing or fitting
bushes to avoid breaking the casing.
17 lnspect the housings for the main
bearings (see illustration 14.16). If a bearing
outer race has spun in its housing, the inside
of the housing will be damaged. A bearing
locking compound can be used to fix the
outer race in place on reassembly if the
damage is not too severe.
18 The crank assembly should give many
thousands of miles of service. The most likely
problems to occur will be worn main bearings
or a worn big-end bearing due to poor
lubrication (see illustration). If the main
bearings have failed, excessive rumbling and
vibration will be felt when the engine is
running. Sometimes this may cause the oil
seals to fail, resulting in poor running.
19 Wash the bearings with a suitable solvent
and dry them with compressed air, then apply
a few drops of light oil inside each bearing. A
bearing should be almost silent when spun; if
it grates or rattles it is worn and must be
replaced with a new one (see illustration).
Always renew both main bearings at the same
time, never individually. Note that it is good
practice to renew the main bearings in the
course of an engine overhaul.
20 A worn big-end bearing will produce a
pronounced knocking noise, most audible
when the engine is under load, and increasing
as engine speed rises. This should not be
confused with small-end bearing wear, which
produces a lighter, metallic rattle. To assess
the condition of the big-end bearing, hold the
crank assembly firmly and push and pull on
the connecting rod, checking for any freeplay
between the two (see illustration). If any
freeplay is noted, the bearing is worn and the
crank assembly will have to be replaced with
a new one.
21 Measure the big-end side clearance with
a feeler gauge (see illustration). If the
clearance is greater than the service limit
specified at the beginning of this Chapter,
renew the crank assembly.
22 Measure the internal diameter of the
connecting rod small end with a telescoping
gauge and compare the measurement to the
specifications at the beginning of this Chapter
14.19 Bearings should be almost silent
14.20 Any freeplay indicates a worn big-
14.21 Measuring big-end side clearance
when spun
end bearing
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