Royal Enfield 500 TWIN 1949 Workshop Maintenance Manual page 55

ROYAL ENFIELD WORKSHOP MANUAL
(iii) Fit the new field coil over the pole shoe
and place it in position inside the yoke. Take
care to ensure that the taping of the field coil is
not trapped between the pole shoe and the yoke.
(iv) Locate the pole shoe and field coil by
lightly tightening the fixing screw, insert the
pole shoe expander (see Fig. 5), open to its
fullest extent and tighten the screw. Remove the
expander and give the screw a final tightening
with the wheel-operated screwdriver. Lock the
screw in position by caulking, that is, by tapping
some of the metal of the yoke into the slot in the
head of the screw.
4. (e). Armature
The testing of the armature winding requires
the use of a voltdrop test or a growler. If these
are not available, the armature should be checked
by substitution. No attempt should be made to
machine the armature core or to true a distorted
armature shaft.
4 (f). Bearings
Ball bearings are fitted to both the
commutator and drive end brackets. When the
bearings become worn to such an extent that
they allow side movement of the armature shaft,
they must be replaced. To replace the ball
bearing at the commutator end proceed as
follows :
(i) Remove the screw from the end of the
armature shaft and, using a caliper type
extractor, draw the bearing off the shaft.
(ii) Wipe out the bearing housing and pack
the new bearing with H.M.P. grease.
(iii) Position the bearing on the end of the
shaft and press it squarely home, applying
pressure on the inner journal of the bearing.
To replace the ball bearing at the drive end
proceed as follows :
(i) Remove the bearing retaining plate from
the drive end bracket as previously described.
(ii) Press the bearing out of the end bracket,
using a metal drift locating on the inner journal
of the bearing. Wipe out the bearing housing and
pack the new bearing with H.M.P. grease.
(iii) Position the bearing in its housing and
press it squarely home, applying pressure on the
outer journal of the bearing.
4 (g). Reassembly
In the main, the reassembly of the dynamo is
a reversal of the operation described in
Subsection 4(b), bearing in mind the following
points :
(i) The field coil lead fitted with the short
length of yellow tubing must be connected,
together with the eyelet of the earthed brush, to
the commutator end bracket by means of the
screw provided.
(ii) The second field coil lead must be
Section G2b Page 4
connected to terminal "F" on the moulded cap
(see Fig. 6).
(iii) The unearthed brush flexible lead must
be connected direct to terminal "D" on the
moulded end cap.
(iv) Take care to refit the cover band in its
original position and make sure that the
securing screw, when of flush-fitting pattern,
does not "short" on the brush gear.
5. Dynamo Polarity
All replacement motor cycle dynamos are
despatched from the Works suitable for
immediate use on positive earth systems. If the
negative terminal of the battery is earthed on the
machine for which the replacement dynamo is
intended, it will be necessary to re-polarize the
dynamo before use to make it suitable for
negative earth.
Similarly, if a dynamo has been incorrectly
connected on the motor cycle and its polarity has
become reversed, then it must be re-polarized.
To do this, fit the dynamo to the motor cycle
but do not at this stage connect the cable to the
"D" and "F" terminals. Temporarily connect a
length of wire to the unearthed terminal of the
battery and hold the other end of this wire in
contact with dynamo terminal "F" for a few
seconds only. This serves to re-polarize the
dynamo. The temporary connection can now be
removed and the original cables connected to
"D" and "F" terminals.
The practice of closing the cut-out points to
reverse the dynamo
recommended, as this method allows a high
initial surge of current from the battery to pass
through the armature, which can damage the
windings, insulation, etc. and result in a
decreased service life of the machine.
Generally speaking, Enfield motorcycles
manufactured up to and including 1951 had the
negative terminal of the battery connected to the
frame. With a few exceptions, i.e. Miller coil
ignition sets and rectifier sets on two-stroke
machines, all Royal Enfield machines in current
production have the positive terminal earthed.
polarity is not