O.S. Engines FS-40S-CX - Manual (Page 20)

Re-tighten locknut while holding adjusting
screw stationary. (Fig.5.) 4.
Hold at the screw head.
Fig.5
Tighten Locknut.
Remove 0.04mm feeler, rotate the
crankshaft through two revolutions and
recheck gap. 5.
If clearance is correct, slacken locknut on
the other rocker-arm and repeat steps 1 to 5
above. Finally, replace rocker box cover. 6.
Remember:
Excessive valve clearance will cause loss of
power, due to valve (s) not opening
sufficiently. On the other hand, a total loss of
clearance may cause difficult starting due to
valves not closing properly, resulting in loss
of compression.
2.
3.
Turn adjusting-screw approx. 1/2 turn counter-
clockwise to open gap, using appropriate tool -
i.e. Allen hex key. (Fig.3.)
Fig.3
Fig.4
Adjusting Screw
Turn approx.
1/2 turn.
Allen Key
Insert 0.1mm feeler gauge between valve
stem and rocker-arm and gently turn adjusting
screw clockwise until it stops.(Fig.4.)
0.1mm Feeler Gauge
Turn with fingers
until it stops.
19