"CRUSADER
250," "250
CLIPPER"
AND
"CRUSADER
SPORTS"
OVERHAULING
THE
ENGINE
21
Decarbonising. When
an
engine has been in use
for some time, carbon deposit forms
on
the piston and
cylinder head and the engine must be partly dismantled
to allow this deposit to be scraped off and the valves to
be re-ground.
The
time when decarbonising becomes necessary
will
be
indicated by
an
increased tendency to
"
pink
"
and
will occur after approximately the first
2,000
to
2,500
miles,
and'
subsequently at intervals of about 5,000
miles.
22 Removal of Cylinder Head.
Turn
off the petrol
tap
and disconnect the petrol pipe from the tank. After
removing the boit attaching the front of the tank to the
frame, the rear of the tank
can
be pulled upwards,
releasing the clip holding it to the
top
tube of the frame,
and the tank lifted clear.
Unscrew
the central nut
securing the rocker box cover, remove the cover
and-
carefully·
-the
gasket. Detach the oil pipe assembly
which leads from the crankcase to the cylinder head.
Remove the exhaust pipe, sparking plug and the cylinder
head steady. Roll back the rubber connection from the
carburettor air intake to the air cleaner and remove the
carburettor from the cylinder head.
Undo
the
five
cylinder head holding down nuts (four inside the rocker
box and one near the sparking plug hole).
Machines having an alloy
head
have an extra securing
pin in the push rod tunnel.
In
addition to removing the
five holding down nuts, also
undo
this pin, which has a
hexagon socket head.
Lift the cylinder head about one inch and remove
the push rods; the head can now
be
lifted clear.
23
Removal of Cylinder and Piston. Whilst it
is
not
strictly necessary to remove the cylinder barrel and piston,
this should preferably be done so
that
the condition of
the piston, rings and big-end bearings can
be
examined.
To
remove the cylinder barrel after removal of the head,
simply lift the barrel off the five long studs.
To
remove
the piston, remove one of the circlips holding the
17
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