Royal Enfield 500 TWIN 1949, Workshop Maintenance Manual

Page: 12 / 110

ROYAL ENFIELD WORKSHOP MANUAL
SECTION C1
Service Operations with Engine in Frame
" Meteor 700" and " 500 Twin"
1. Removal of Timing Cover
First place a tray under the engine to catch
the oil which will escape when the cover is
removed. Remove the timing side exhaust pipe
and the oil filler neck by taking out the three
screws fixing it to the crankcase. Remove the
timing cover fixing screws. Draw off the timing
cover, tapping it lightly if necessary.
In refitting the cover, insert the two long
screws through the cover to locate the gasket.
See that the thrust washer is on the chain
tensioner sprocket spindle and that the rubber
seal is in the hole in the oil pump worm.
Replace this seal if it is damaged or at each
service to ensure oil pressure to the big end
bearings.
When refitting the cover it is important that
the engine is turned gently forwards while the
cover is being put into place. This will help the
engagement of the pump worm with the pump
spindle and prevent damage to the gears.
To verify that the oil pumps are working
after replacing the timing cover, start the engine
up and remove the oil filler cap so that the oil
return pipe can be seen.
2. Valve Timing
The camshaft sprockets are keyed to the
camshafts so that the valve timing can only be
incorrect if the timing chain is maladjusted.
The correct setting is obtained with the
marks stamped on the camshaft sprockets facing
each other inwards on the centre line and the
mark on the crankshaft sprocket pointing
vertically downwards (see Fig. 3). If it is
necessary to remove the sprockets, see
Subsections 23 and 24.
Remember that all three timing sprocket
fixing bolts have Left Hand Threads. While
tightening the camshaft bolts the sprockets
should be held.
The correct valve timing at .012 in.
clearance is as follows:-
Exhaust Opens 75° before bottom dead centre.
Exhaust Closes 35° after top dead centre.
Inlet Opens 30° before top dead centre.
Inlet Closes 60° after bottom dead centre.
3. Tappet adjustment
The tappet clearance is adjusted by means of
a screw in the outer end of each rocker. Access
to the adjusting screws is obtained by removing
the covers of the rocker boxes.
The clearance between the end of the screw
and the valve stem cap should be nil or as little
as possible with the engine COLD.
To adjust the clearance, loosen the locknut
beneath the rocker arm, turn the screw with a
small spanner and re-tighten the locknut.
The adjustment for each valve should be
made with the corresponding valve of the other
cylinder fully open. This ensures that the tappet
is well clear of the ramp which is located on
either side of the cam to reduce valve noise.
If, after long service, the valve stem cap or
the rocker adjusting screw is found to be worn,
they should be renewed, as uneven thrust, due
to the screw being in a different position after
adjustment, may cause lateral movement of the
rocker, giving rise to a sharp tapping noise.
4. Ignition Timing
Magdyno. The setting of the ignition
depends upon the position of the sprocket
relative to the magneto shaft.
To obtain access to the magneto sprocket it
is necessary to remove the timing cover.
The sprocket is mounted on a smooth taper
on the magdyno shaft and is held in position by
a nut
(Right Hand Thread). To remove the
sprocket, undo the nut and use a suitable
extractor.
Before setting the timing, adjust the contact
breaker points to a clearance of .012/.015 in.
when fully opened and put the ignition lever in
the full advance position. See that the screw in
the magneto ring is in the end of the slot and
that it is not sticking.
To set the timing, turn the "Meteor" engine
until the left hand piston is 3/8 – 7/16 in. before
top dead centre on the compression stroke, i.e.
with both valves closed.
Insert a piece of thin tissue paper between
the points of the contact breaker and turn the
magneto forwards until the paper can just be
pulled out, making sure that the magneto rotor
is in the position to cause a spark on the left
hand cylinder sparking plug. Give the sprocket
a sharp tap to secure it on the shaft and then
lock it by tightening the nut.
Section C1 Page 1
www.hitchcocksmotorcycles.com