Royal Enfield 500 TWIN 1949 Workshop Maintenance Manual page 13

ROYAL ENFIELD WORKSHOP MANUAL
The 500 c.c. engine has a shorter stroke and
the timing should therefore be set at 5/16 - 3/8
in. before top dead centre.
Coil Ignition. On earlier models a dynamo
and distributor were fitted, instead of the
magdyno, and coil ignition was used. The
distributor includes an automatic advance
mechanism which is normally in the "retard"
position when the engine is stationary.
The correct setting for the timing is for the
contact breaker points to open when the pistons
are 1/32 in. after top dead centre.
Before setting the timing, remove the rotor
arm of the distributor and adjust the contact
breaker points to a clearance of .014/.016 in.
An approximate setting can be obtained by
engaging the most suitable tooth on the dynamo
sprocket with the chain when re-assembling the
engine or by slackening the screw securing the
distributor and replacing it in a different tooth of
the skew gear drive. The flat side of the
distributor body should be lined fore and aft to
avoid the terminal screw fouling the air cleaner.
Make sure that the rotor arm of the distributor
is pointing towards the contact connected to the
plug lead of the cylinder which is on
compression, i.e. with both valves closed.
The fine adjustment of the timing is made by
turning the engine until the pistons are 1/32 in.
after top dead centre and then (having slackened
the securing screw A) rotating the distributor
body until the contact breaker points are just
opening. Then tighten the securing screw.
This point can be determined by inserting a
thin piece of tissue paper between the contact
Section C1 Page 2
breaker points and turning the distributor
housing until the paper can just be drawn out.
An alternative method is to remove the cap
from the plug lead and tuck the lead between the
fins of the cylinder. Switch on the ignition and
rotate the distributor until a spark is seen at the
instant the points open. Move the distributor
body clockwise to retard the timing and
anticlockwise to advance it.
5. Primary Chain Adjustment
Access to the primary chain adjuster is gained
by removing the primary chain cover, which is
held in position by a single nut. Before removing
the nut, place a tray under the engine to catch the
oil from the chain case.
Beneath the bottom run of the chain is a
curved slipper on which the chain rests and
which may be raised or lowered by turning the
adjusting screw after having first slackened the
locknut.
To take up slack in the primary chain, unscrew the locknut
and turn the adjuster beneath the curved slipper until correct
chain tension is obtained ; re-tighten the locknut.
On the "Meteor" engine a rubber button is
fitted to the end of the adjusting screw to prevent
the transmission of chain noise to the chaincase
and this is held against the chain case and
bouncing is prevented by a hairpin spring. This
is not necessary on the "500 Twin" because the
chain line is different on account of the smaller
sprocket.
After replacing the chain cover, remember to
replenish the chain case with oil.
Do not adjust the chain to be dead tight but
rotate the engine slowly, and, while doing so,
test the tension of the top run of the chain by