O.S. Engines 25LA - Manual (Page 20)

Check that the throttle is one-third open from the fully
closed position. Bring the starter into contact with the
spinner nut or spinner and depress the starter switch
for one or two seconds. Repeat if necessary. When
the engine fires, withdraw the starter immediately.
Attention: Never place your finger over the
carburettor intake when applying the starter. Such an
action will cause an excess quantity of fuel to be
drawn into the cylinder and result in hydraulic lock
that may damage the engine.
BEWARE of
the rotating
propeller.
14 Engine starts
If the engine does not start, refer to the TROUBLE
SHOOTING CHART on page 26- 27.
In the interests of safety, keep your face and other parts of the
body away from the vicinity of the propeller.
Listen to the sound
carefully.
15 Needle-valve adjustment(1)
Slowly advance throttle to its fully open position, then gradually
close the needle-valve until the exhaust sound changes pitch.
Close the needle-valve gradually until a high-pitched exhaust
note begins to be superimposed on the lower-pitched sound.
19