Dismantling Cylinder Head
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Remwe fiom the tappet block~.
Cylinder Block. Unscrew the eight nuts; secure the tappets in the blocks by
placing a rubber
wc.dge between them, taking care not to use undue force. Carefully
lift the cylinder block off the pistons.
Pistons.
Remove a circlip from each piston and then press the gudgeon pins out
from the opposite end.
The
fit
of the gudgeon pins in the pistons
is
fairly tight;
if a gudgeon pin extractor is available,
it
should be employed. The pistons should
be suitably marked on the inside to ensure replacement to their original positions.
Magneto or Distributor. Unscrew the securing nuts and remove the unit.
Crankcase bolts. Remove the remaining bolts and screws. NOTE.-Do not
forget to remove the two screws from the internal bosses.
Crankcase Filter.
Slacken off the vice jaws and remove the crankcase. Unscrew
the four nuts holding the filter base and remove the base and filter gauze.
Crankshaft and Camshafts. To split the crankcase, bump the drive shaft onto a
piece of wood when the two halves will readily part. The crankshaft and camshafts
can now be removed.
In the drive side crankcase the breather rotary valve and spring
is
located in the
camshaft bush.
Care should be taken not to lose these.
DISMANTLING, PREPARATION AND ASSEMBLY OF
THE ENGINE UNITS
CYLINDER HEAD
Rocker Boxes. Unscrew the four nuts and then the four screws when the rocker
boxes can be removed from the head. Wash the rocker boxes thoroughly and inspect
the parts for wear. Check the ball ends, adjuster pins, and rockers on the spindles
for wear.
Examine the rocker boxes for cracks or pulled studs.
Normally, wear
on the rocker spindles
is
negligible
as
they are fully lubricated.
The adjuster pins
sometimes show slight wear
or
indentation which can be removed by lightly stoni;lg
the hardened pad. If the markings are too deep, the pins should be replaced.
Carefully inspect the ball ends, if the spheres are mis-shapen the bail ends must be
changed. This operation will necessitate dismantling the rocker box or boxes.
To do this, knock out the rocker spindle from the threaded end using a hide hammer
or similar softtooi to prevent damage to the thread. After withdrawing the rocker
levers the ball ends can be pressed out of the housings and the new ball-ends fitted.
When replacing the spindles, a new rubber seal must be employed: Fig.
6
shows
the position of the various washers.
Valves and Springs.
Compress the valve springs sufficiently with
a
compressor
too!, when the split cotters can be ezsed away with a narrow screwdriver or similar
tool.
Release the tool and withdraw both valve and valve springs.
Repeat the
operation
to
the other valves; mark the valves for replacement. Inspect the springs
for signs of fatigue (Free length Outer,
2.031"
(5.16 cms.); Inner, 1.625" (4.13 cms.)
);
if in doubt,
a
new
set
of springs should be obtained.
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