Royal Enfield SPRING FRAME O.H.V. 250cc CLIPPER 1954 Workshop Maintenance Manual page 21

ROYAL ENFIELD WORKSHOP MANUAL
On some early engines with Miller equipment
the rotor may have two keyways. In this case care
should be taken when reassembling to fit the key
in the keyway previously and to reassemble the
rotor the same way round. If this is not done the
efficiency of the Emergency Starting may be
affected.
25. Pressure Relief Valves.
There are two pressure relief valves in the oil
feeds to the big end and to the rocker gear respec-
tively. Their function is to prevent excessive
pressure and their setting is not critical. The feed
to the rocker gear comes from the return oil from
the crankcase to the tank.
The pressure relief valves are set before leaving
the Works and should not normally require to be
disturbed. If, however, it is found necessary to
dismantle either of them, they can be reset as
follows:-
Rocker Feed Relief Valve. This is located in
the oil tank immediately below the oil filler cap
socket and consists of a 3/16 in. steel ball held in
position by a spring and brass plug (see Fig. 6).
To gain access to it, take out the securing peg
of the oil filler cap socket and remove the socket.
The valve should be set so that oil just reaches
the rockers when the engine is running slowly.
Great care must be taken not to drop the plug,
the spring or the ball into the oil tank. A small
magnet is useful for extracting the springs and ball
or a rod with stiff grease on the end.
Section C3 Page 8
Big End Relief Valve. This is located in the
timing-side crankshaft and can only be adjusted
when the crankshaft has been dismantled. It consists
of a 5/16 in. dia. steel ball and spring held in
position by a screwed plug.
The valve is set to open when the oil pressure
exceeds about 35 lbs. per square inch and when set
correctly there is a movement of about 3/32 in. of
the ball off the seat. This can be measured without
dismantling the crankshaft by pushing a thin rod
through the hole in the pump worm with the oil feed
plug in the timing cover removed.
If the crankshaft is dismantled for any reason, it
is always advisable to fit a new spring to the relief
valve in case the original one has become weak.
If the valve is set to give too high a pressure, the
pump disc will be forced off its seating.
26. Removal of Contact Breaker Housing
and Bracket.
Disconnect the lead to the switch.
Remove the contact breaker pinion (Sub-section
18).
Lucas Equipment. The contact breaker housing
is attached to the housing bracket by one round
headed screw and if this is removed the housing can
be withdrawn.
The bracket can be detached from the crankcase
by removing two hexagon headed fixing bolts.
Miller Equipment. Slacken the nut on the
securing strap and withdraw the contact breaker and
housing complete.