ROYAL ENFIELD 350cc O.H.V. WORKSHOP MANUAL
Page 9
the inlet and exhaust valves, as there is a difference
of .002 in. in the stem diameter.
9. Reassembly of Engine after Decarbonising.
When reassembling the engine, take great care to
have all parts perfectly clean and put clean oil on the
piston, particularly round the rings. The cylinder base
joint must be made with a paper washer which must
have a small hole in it registering with the oil feed to
the back of the cylinder. The cylinder head joint may
be made with the old copper washer which, however,
should preferably be annealed by heating to red heat
DETAIL OF JOINTS IN PUSH ROD
ENCLOSURE TUBES
Fig. 6
then quenching. New Hallite washers painted with
gold size or shellac should be fitted to make the joints
in the push rod enclosure tubes (see Fig. 6). When
tightening down the cylinder base nuts, work
diagonally from one to another to ensure pulling the
base down dead level. When tightening down the
cylinder head nuts put pressure first of all on the two
at the push rod side of the engine so as to ensure
compressing the push rod enclosure tube washers
thoroughly and bringing even pressure on the copper
head gasket. When replacing the valve rockers and
caps put a little oil on each rocker and make sure that
the rocker is free after the cap has been tightened
down. If necessary, a sharp tap on the end of the
rocker will usually free it. Excessive play in the
rocker bearings can be taken up by grinding a little
metal from the lower face of the hardened cap. Very
little grinding is required and not more than .001 in.
should be taken off at a time. When replacing the
rocker box cover, a new joint washer should be used.
The cylinder head and base nuts should be
checked again for tightness, after the engine has
been run long enough to get it thoroughly warm.
TIMING GEAR.
10. Valve Timing.
Access to the timing gear is obtained by removal
of the timing cover after unscrewing the nine nuts
securing it. About half a pint of oil will run out of the
timing case. The cam wheels and magdyno drive idler
pinions can now be pulled off their spindles, having
first turned the engine so that both valves are closed.
Correct timing is obtained when the tooth on the
exhaust cam wheel having two dots on it meshes with
the space having two dots on the small timing pinion,
while at the same time the tooth having one dot on the
inlet timing wheel meshes with the space having one
dot on the exhaust timing wheel (see Fig. 7). In case
VALVE TIMING MARKS
Fig. 7
the two dots on the small timing pinion are covered by
one corner of the hexagon on the oil pump driving
worm, note that when the piston is at the top of the
compression stroke, the single dots on the timing
wheels lie on the line joining the centres of the two
cam spindles. When replacing the magdyno drive
idler pinions note that there is a hardened steel washer
on either side of each pinion and that the deeper boss
on the pinion is outwards. If the cam wheels have thin
shims on either side take care to replace these on the
same spindles.
11. Magneto Timing.
The magneto timing is not marked and must be
set as follows:- Unscrew the nut which holds the
timing pinion on to the magdyno shaft. Then screw
the pinion extractor (supplied in the tool kit) into the
centre of the timing pinion, thus loosening it from its
taper (see Fig. 8). Remove the extractor, set the
engine so that the piston is at the top of its
compression stroke (seen by removal of the cylinder
head or gauged by means of a narrow rule or timing
stick passed through the sparking plug hole), see that
the contact points open to the correct figure of .012 in.
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