O.S. Engines FS-26S-CX - Manual (Page 18)

Note:
Valve clearances of all O.S. four-stroke-
cycle engines must be checked and reset
ONLY WHEN THE ENGINE IS COLD.
Procedure is as follows.
Remove the cover from the rocker-box on
top of the cylinder-head, using the correct
size Allen hex key. 1.
( 1 )
Turn the flywheel counter-clockwise until
compression is first felt, then turn it a further
quarter revolution. At this point, both valves
should be closed. (If the prop driver ('drive
hub') of your engine is engraved with a letter
'T', this mark should now be at the top.) 2.
The standard valve clearance, on both inlet
and exhaust valves, is between 0.04mm and
0.10mm(0.0015-0.004 inch), measured
between valve stem and rocker arm. Use the
0.04mm and 0.10mm feeler gauges to check
clearances.
(See Fig.1.) 3.
Fig.1
0.04mm Feeler Gauge
Rocker Arm
Valve
• Feeler gauge 0.04mm
ALL O.S. four-stroke engines have their
valve(tappet) clearances correctly set before
they leave the factory. However, if, after many
hours of running time have been logged, a loss
of power is detected, or if the engine has to be
disassembled or repaired as a result of an
accident, valve clearances should be checked
and readjusted, as necessary. O.S. Valve
Adjusting Tool Kit is available as optional
accessory.
VALVE ADJUSTING
The kit comes in a plastic case and includes:
(Code No.72200060)
• Feeler gauge 0.1mm
• Hex. key 1.5mm
• Wrench 5mm
• Screwdriver
17