O.S. Engines FS-26S-CX - Manual (Page 19)

Note:
If the gap is found to be less than 0.04mm,
it is not necessary to readjust the clearance
if the engine has good compression and
starts easily. Equally, if the gap exceeds
0.10mm but is not more than 0.14mm (i.e.
the thickness of both feeler gauges inserted
together), it is not essential to readjust the
clearance if the engine runs satisfactorily.
( 2 )
If a clearance is found to be outside either of
these limits, it should be reset as follows.
Carefully loosen locknut on rocker-arm 1/4-
1/2 turn with a 5mm wrench. (Fig.2.) 1.
2.
3.
Locknut
Wrench
Slacken approx. 1/4 to 1/2 turn.
Turn adjusting-screw approx. 1/2 turn counter-
clockwise to open gap, using appropriate tool -
i.e. Allen hex key. (Fig.3.)
Fig.2
Fig.3
Fig.4
Adjusting Screw
Turn approx.
1/2 turn.
Allen Key
Insert 0.04mm feeler gauge between valve
stem and rocker-arm and gently turn adjusting
screw clockwise until it stops.(Fig.4.)
0.04mm Feeler Gauge
Turn with fingers
until it stops.
18