Royal Enfield 500 TWIN 1949, Workshop Maintenance Manual

Page: 47 / 110

ROYAL ENFIELD WORKSHOP MANUAL
Section G2a Page 2
2 (b). Inspection of Commutator and
Brushgear
About once every six months remove the
cover band for inspection of commutator and
brushes, see Subsection 4 (a) (vi).
3. Test Data
Cutting-in Brush
Speed Output Field Spring
(Dynamo Cold) Test Resistance Tension
1,000-1,150 10 amps. at 2.6-2.8 16-20 oz.
r.p.m. 1,700-1,850 ohms
at 6.5 volts r.p.m.
at 7 volts*
*On resistance load of 0-7 ohm.
4 (a). Testing in Position to Locate Fault in
Charging Circuit
In the event of a fault in the charging circuit,
adopt the following procedure to locate the
cause of the trouble.
(i) Check that the dynamo and regulator
units are connected correctly. The dynamo
terminal "D" should be connected to the
regulator unit terminal "D" and dynamo
terminal "F" to regulator terminal "F."
(ii) Remove the cables from the dynamo
terminals "D" and "F" and connect the two
terminals with a short length of wire.
(iii) Start the engine and set to run at normal
idling speed.
(iv) Connect the negative lead of a moving
coil voltmeter, calibrated 0-10 volts, to one of
the dynamo terminals and connect the positive
lead to a good earthing point on the dynamo
yoke or engine.
(v) Gradually increase the engine speed,
when the voltmeter reading should rise rapidly
and without fluctuation. Do not allow the
voltmeter reading to rise above 10 volts and do
not race the engine in an attempt to increase the
voltage. It is sufficient to run the dynamo up to a
speed of 1,000 r.p.m. If there is no reading,
check the brush gear, as described in (vi) below.
If there is a low reading of approximately 1/2
volt, the field winding may be at fault, see
Subsection 4 (d). If there is a reading of
approximately 1.1/2 to 2 volts, the armature
winding may be at fault, see Subsection 4 (e).
(vi) Remove the cover band and examine the
brushes and commutator. Hold back each of the
brush springs and move the brush by pulling
gently on its flexible connector. If the movement
is sluggish, remove the brush from its holder and
ease the sides by lightly polishing on a smooth
file. Always replace brushes in their original
positions. If the brushes are worn so that they do
not bear on the commutator or if the brush
flexible is exposed on the running face, new
brushes must be fitted.
Test the brush spring tension with a spring
scale (see Fig. 2). The correct tension is 16-20
oz. and new springs must be fitted if the tension
is low.
If the commutator is blackened or dirty, clean
it by holding a petrol-moistened cloth against it
while the engine is turned slowly by means of
the kick start (with sparking plugs removed).
Re-test the dynamo as in (v) above. If there is
still no reading on the voltmeter, there is an
internal fault and the complete unit should be
replaced if a spare is available. Otherwise the
unit must be dismantled, see Subsection 4 (b) for
internal examination.
(vii) If the dynamo is in good order, restore
the original connections. Connect regulator unit
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