Royal Enfield 500 TWIN 1949, Workshop Maintenance Manual

Page: 39 / 110

ROYAL ENFIELD WORKSHOP MANUAL
sintered iron which will absorb sufficient oil
from the oil feed to the helical driving pinion.
Automatic timing control. Unscrew the two
screws securing the contact breaker base plate to
the distributor body and lubricate the timing
control mechanism with thin machine oil, paying
particular attention to the pivots. Refit the base
plate.
No grease or oil must be allowed to get on
or near the contacts when carrying out the
foregoing procedure.
(ii) Cleaning. To be carried out every 6,000
miles. Wipe the inside and the outside of the
cover moulding with a soft dry cloth. Pay
particular attention to the spaces between the
metal electrodes and check that the small carbon
brush moves freely in its holder.
Examine the contact breaker. The contacts
must be free from grease or oil. If they are burnt
or blackened, clean them with a fine
carborundum stone or very fine emery cloth,
afterwards wiping away any trace of dirt or metal
dust with a petrol-moistened cloth. Cleaning of
the contacts is made easier if the contact breaker
lever carrying the moving contact is removed. To
do this, unscrew the nut securing the end of the
contact breaker spring and remove the nut,
spring washer and bush. Lift the contact breaker
lever off its bearing. After cleaning check the
contact breaker gap setting.
(iii) Contact breaker setting. Contact breaker
gaps should be checked every 3,000 miles. If the
gap is allowed to decrease below the specified
setting, rapid and excessive pitting and piling
may occur.
Turn the engine until the contacts are seen to
be fully opened and check the gap with a gauge
having a thickness of .014 - .016 in. If the gap is
correct the gauge should be a sliding fit but if
the gap varies from the gauge, the setting must
be adjusted.
To do this, keep the engine in the position
giving maximum contact opening and slacken
the two screws securing the fixed contact plate.
Adjust the position of the plate until the gap is
set to the thickness of the gauge and tighten the
two locking screws.
2 (b). High Tension Cables
Examine the high tension cables. Any, which
have the insulation cracked or perished, or show
signs of damage in any other way, must be
renewed, using neoprene covered rubber
ignition cable.
3. Servicing
3(a).
Testing in Position to Locate Ignition Fault
If a failure of ignition or misfiring occurs,
first make sure that the trouble is not due to
defects in the engine, carburetter, petrol supply,
sparking plug(s), etc. If necessary adjust the
sparking plug gaps to .018 - .020 in. This must
be done by bending the earth points only,
not
the central electrode. Ensure also that the
battery is not discharged.
(i) Examine the high tension cables. If the
rubber shows signs of deterioration or cracking
the cable should be renewed using neoprene
covered high tension cable.
(ii) Test each plug and high tension cable by
removing the plug and allowing it to rest on the
cylinder head and observing whether a spark
occurs at the points when the engine is turned. It
should, however, be noted that this is only a
rough test, since it is possible that sparking may
not take place when the plug is under
compression.
(iii) Examine the contact breaker, checking
the gap setting and measuring the contact
breaker spring tension. This should be 20-24 oz.
measured at the contacts.
(iv) Switch on the ignition, turn the engine
and observe the ammeter reading. If an ammeter
reading is given which rises and falls with the
closing and opening of the contacts the low
tension wiring is in order. If the reading does
not fluctuate in this way a short circuit in the
low tension wiring is indicated.
Check the capacitor (condenser) and ignition
coil for short circuit by substitution. Examine
the insulation of the contact breaker.
When no reading is given a broken or loose
connection in the low tension wiring is
indicated. Refer to the wiring diagram and
examine the connections to the ignition switch.
Check the ignition coil by substitution.
Remove the high tension cable from the
centre distributor terminal. Switch on the
ignition and turn the engine until the contacts
close. Flick the contact breaker lever open while
the high tension lead from the coil is held about
3/16 in. away from the cylinder block. If the
ignition equipment is in order a strong spark
should be obtained. If no spark is given it
indicates a fault in the circuit of the secondary
winding of the coil and the coil should be
replaced.
3 (b). Dismantling the Distributor
Spring back the securing clips and remove
the moulded cover (see Fig. 2). Lift the
moulded rotor arm off the top of the spindle.
Withdraw the two securing screws and lift off
the contact breaker base.
Unscrew the nut on the moving contact pillar
and remove the spring washer and bush. Lift off
the contact breaker spring and contact breaker
arm. The fixed contact is secured on a plate by
Section G1a Page 2
www.hitchcocksmotorcycles.com