Royal Enfield CONSTELLATION 1958, Workshop Maintenance Manual

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tube of 9/16 in. internal diameter to prevent
damage to the bore of the guide. If a valve
guide is removed for any reason, an oversize
one should be fitted in order to maintain the
interference. It is necessary to re-cut the valve
seat and grind in the valve after a guide has
been replaced. (See Subsection 18.)
A worn exhaust valve guide may give rise to
slight smoking from the exhaust pipe due to oil
passing down the valve stem on to the hot valve
head. This may also be caused or increased by
faulty operation of the breather.
14. Removal of the Sparking Plugs
Care must be taken when removing and
replacing the sparking plugs not to damage the
threads in the cylinder heads.
If the threads do become damaged, they can
be tapped out to a larger size and steel wire
inserts fitted.
Special tools are available for tapping and
inserting the steel wire inserts. The latter tool
consists of a piece of 7/16 in. diameter tube or
rod with a slot cut in the end.
The insert is placed over the tool with the tag
engaging in the slot and it is screwed into the
plug hole in the cylinder head from the outside
until the last coil is 1 to 1.1/2 threads below the
top face. A reverse twist of the tool will then
break off the tag.
If the cylinder head has been removed, the
fitting of the insert will be facilitated if the tool
is put through the hole from the inside and the
insert screwed back from the outside.
If the cylinder head has not been removed,
care must be taken not to drop the end of the tag
into the cylinder and in such a case it is better to
break off the tag with a pair of long-nosed
pliers.
Note: Engines with a Number prior to
SMSA 6800 have short reach plugs, in which
case wire inserts are fitted as standard.
15. Removal of the Cylinders
When the cylinder heads have been removed
the cylinders can be lifted clear of the studs. This
should be done with the pistons at top dead
centre.
It is advisable to put a clean cloth over the
mouth of the crankcase to prevent anything,
such as a piece of broken piston ring, from
falling in.
When replacing the cylinders, clean off the
joint faces and fit new paper joints, two to each
cylinder.
16. Removal of Pistons
Remove the cylinder heads and cylinders.
With a tang of a file remove the two outer
circlips retaining the gudgeon pins. Remove the
springs. Withdraw the valve and place its
springs, top spring collar (and bottom collar if it
is loose) and split collets together in order that
they may be re-assembled with the valve from
which they were removed.
Deal similarly with the other valves in the
heads.
If the valve will not slide easily through the
valve guide, remove any slight burrs on the end
of the valve stem with a carborundum stone. If
the burrs are not removed and the valve is forced
out, the guide may be damaged.
12. Removal of the Rockers
To remove the rocker, first take off the
cylinder head. Remove the hexagon plug on the
inner side, and the rocker spindle may be drawn
out by means of a bolt screwed into the rocker
spindle, which is tapped 5/16" B.S.F.
On re-assembling make sure that the spring
washers are fitted on the sides of the rockers
nearest the centre of the engine and the plain
thrust washers on the outer sides.
13. Removal of the Valve Guides
To remove the valve guides from the heads
two special tools are required which can easily
be made.
The first is a piece of tube with an internal
bore of not less than 7/8 in.
The second is a mandrel about 4 in. long
made from 9/16 in. diameter bar with the end
turned down to about 5/16. diameter for 1/2 in.
Support the cylinder head on the tube which
fits over the collar of the valve guide. Using the
mandrel force the guide out of the head with a
hand press or by using a hammer.
To fit a new guide, support the head at the
correct angle and use a hand press and the same
mandrel. If a hand press is not available and the
guide is replaced by a hammer, use a piece of
Section C11 Page 4
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