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(e) When the engine has been fully run-in, the bore will have a highly
polished and very hard surface If new rings are fitted without the
cylinder being rebored or resleeved. the new rings will not bed in
satisfactorily Under these conditions the cylinder should be removed
and the hard polished bore lightly roughened using a medium grade
emery cloth The roughening should be carried out radially by hand and
should be sufficient only to produce a matt surface on the bore.
Alternatively, a suitably sized de-glazing too! of the rotary brush type
with silicone-carbide tips may be used provided method used is in
accordance with manufacturers instructions After this treatment the
cylinder must be thoroughly washed in petrol or paraffin to remove all
traces of carborundum
(f) To allow the piston rings to bed in satisfactorily it is recommended that
the engine be run on half load whenever possible after overhaul.
41. To replace cylinder and piston
(a) Generally reverse the instructions for removal and dismantling
(b) Take care that the piston ring gaps are not in line but well distributed
around the piston circumference
(c) Replace the shims between the cylinder and crankcase. The thickness
of the shims controls the bumping clearance between the piston and
cylinder head at TDC.
(d) Check the bumping clearance (see Technical Data). See To replace
cylinder head
(e) After completing reassembly, check the valve rocker clearance.
42. To examine connecting rod
(a) Drain the sump
(b) Remove the cylinder head. cylinder and sump
(c) Grasp the large end of the connecting rod and check for undue play or
shake in the bearing The flywheel should be rocked backwards and
forwards during this operation
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