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ROYAL ENFIELD 350cc and 500cc O.H.V. WORKSHOP MANUAL
at the commutator end while unscrewing the
bolts and take care not to lose the nuts.
(v) Draw the drive end bracket complete with
armature "E" out of the yoke.
(vi) Remove the nut "R" and press the
armature out of the drive end bracket by means
of a hand press.
(vii) Remove the bearing retaining plate "P"
from the end bracket. This is secured by two
screws and a long threaded bolt.
(viii) Take out the screw securing the green
field coil lead with the yellow sleeve to
commutator end bracket and remove the end
bracket "Q" withdrawing the connectors through
the slot in the insulating plate.
(ix) Unscrew the three screws securing the
insulating plate to the commutator end bracket
and remove the plate with brush gear.
4 (c). Commutator
Examine the commutator. If it is in good
condition it will be smooth and free from pits or
burnt spots. Clean with a petrol-moistened cloth.
If this is ineffective, carefully polish with a strip
of very fine glass paper while rotating the
armature.
To remedy a badly worn commutator, mount the
armature with or without the drive end bracket
in a lathe, rotate at high speed and take a light
cut with a very sharp tool. Do not remove more
metal than is necessary. Polish the commutator
with very fine glass paper.
Undercut the insulation between the segment,
to a depth of 1/32 in. with a hacksaw blade
ground down until it is only, lightly thicker than
the insulation (see Fig. 3.)
4 (d) Field Coil
Measure the resistance of the held winding
by means of an ohm-meter. It this is not
available connect a 6-volt D.C. supply with an
ammeter in series with the coil. The ammeter
reading should be approximately 2 amps. No
reading on the ammeter indicates an open circuit
in the field winding.
To check for an earthed coil, connect a main,
test lamp between one end of the coil and the
yoke. If the bulb lights, there is an earth between
coil and yoke.
In either case, unless a replacement dynamo is
available, the field coil must be replaced but this
should only be attempted if a wheel-operated
screwdriver and pole shoe expander are at hand,
the latter being especially necessary to ensure
that there will be no air gap between the pole
shoe and the inner face of the yoke.
To replace the field coil, proceed as follows
(i) Unscrew the pole shoe retaining screw by
means of the wheel-operated screwdriver (see
Fig. 4).
(ii) Draw the pole shoe and field coil out of
the yoke and lift off the coil.
Page 35
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