Royal Enfield CONSTELLATION 1958, Руководство по техническому обслуживанию мастерской

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cup and with a backwards and forwards rotary
motion, grind it on to its seat. Alternatively, a
tool which pulls on the valve stem can be used.
Frequently lift the valve and move it round so
that an even and true seating is obtained. If no
light spring is available, the lifting will have to
be done by hand. Continue grinding until a
bright ring is visible on both valve and seating.
The faces and seats of the exhaust valves are
cut at 45 degrees but the profiles of the inlet
valves are of a special streamlined design which
eliminates pockets and sharp edges and allows a
smooth flow of gas without eddies.
If the inlet valves or their seats are pitted and
require recutting, care must be taken to
reproduce the correct profile as shown in Fig. 6.
The cylinder heads should preferably be
returned to the Works for the inlet valve seats to
be re-cut, but, if this is not possible, a special
tool consisting of an arbor No. T 2053 and cutter
No. T2054 is available. Great care must be
exercised in using this tool as it is located off the
long central cylinder studs which come opposite
the gudgeon pins.
Use Special Tool No. E.5477 to extract the
gudgeon pin or using a rod about 1/4 in. in
diameter insert this right through one gudgeon
pin and drive the other pin out of its piston,
supporting the connecting rod substantially
meanwhile to prevent distortion.
Having lifted the first piston away, the other
one may be readily removed in the same
manner. Mark the pistons and gudgeon pins so
that they go back into the same pistons the same
way round and so that the pistons go back into
the same barrels the same way round.
Take care not to drop the gudgeon pin circlip
into the crankcase. A clean cloth should be put
over the mouths of the crankcase to prevent this.
17. Decarbonising
Having removed the cylinder heads as
described in Subsection 10, scrape away all
carbon, bearing in mind that you are dealing
with aluminium which is easily damaged.
Scrape gently and avoid scoring the combustion
chamber or the valve seats which are of
austenitic iron shrunk into the head. Be careful
while performing this work not to injure the
joint faces which bed down on to the head
gaskets.
Do not, in any circumstances, use caustic
soda or potash for the removal of carbon from
aluminium alloy.
Scrape away all carbon from the valve heads
and beneath the heads, being very careful not to
cause any damage to the valve faces.
If the piston rings are removed the grooves
should be cleaned out and new rings fitted. For
cleaning the grooves, a piece of discarded ring
thrust into a wooden handle and filed to a chisel
point is a useful tool.
If the piston ring gaps exceed 1/16 in. when
the rings are in position in the barrel, new rings
should be fitted. The correct gap for new rings
is .011-.015 in. The gap should be measured in
the least worn part of the cylinder, which will be
found to be the extreme top or bottom of the
bore.
While the cylinders and pistons are not in
position on the engine, cover the crankcase with
a clean cloth to prevent the ingress of dust and
dirt of all kinds. Do not, of course, attempt to
scrape the carbon from the pistons when the
mouths of the crankcase are open.
18. Grinding-in Valves
To grind a valve, smear the seating with a
little grinding in compound, place a light, short
coil spring over the valve stem and beneath the
head, insert the valve into its appropriate guide,
press it on to the seat using a tool with a suction
Section C11 Page 5
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