Royal Enfield 350 BULLET 1989, Workshop Maintenance Manual

Page: 15 / 114

WORKSHOP MANUAL BULLET
Page 15
8. Valves, Valve Guides and springs
VALVE & SPRING ASSEMBLY
Wear on the valve stems can be seen on examination
and if a definite step has formed, the valves should be
renewed. Before replacing the valves, they must be
ground on to their seats, if good faces are not formed with
a reasonable amount of grinding, the seats must be cut
with a cutter (included angle 90°) and the valve refaced in
a universal grinder. Do not attempt to form good seats by
an excessive amount of grinding. This will cause
pocketing and restrict the flow of gases. If a pocket has
already been formed this must be removed by cutting with
a valve seat cutter larger in diameter than the valve head.
Test the valve guides for wear by trying the fit of a new
valve in them. Both valves should be quite free, but the
exhaust valve has more clearance (.002") than inlet valve.
To remove the valve guides from the head, two special
tools are required which can be easily made. The first is a
piece of tube with an internal bore of not less than 7/8".
The second is a mandrel about 4" long made from 9/16"
diameter bar with the end turned down to 1/3" diameter
for a length of 1/2". Support the cylinder head on the tube
which fits over the collar of the valve guide. Using the
mandrel, force the guide out of the head with a hand press
or by using a hammer.
To fit a new guide, support the head at the correct angle
and use a hand press and the same mandrel. If a hand
press is not available, the guide can be replaced using a
hammer and a mandrel, to prevent damage to the guide.
Check the length of the valve springs which are
originally 2.020" and 2.095" for the inner and outer
springs respectively. If these have reached the specified
service limits, they should be renewed.
9. Decompressor
If the decompressor holds compression and operates
freely, there is no need to interfere with it except to
remove the carbon from the head of the valve. If the valve
is leaking, it will be necessary to regrind it on its seat.
This can be done without completely dismantling it.
Having disconnected the control cable from the handle
bar, unscrew the decompressor from the cylinder head.
Compress the spring and remove the spring cap. Unscrew
the adjusting screw and locknut from the cable block and
pull the cable sideways out of the block. Push the spring
DECOMPRESSOR ASSEMBLY
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