O.S. Engines 108FSR - Manual (Page 18)

20
~
45
°
Needle-valve adjustment diagram
This diagram is for reference
purposes only.
Actual needle positions may
differ from those shown.
To stop the engine, close the
throttle completely to cut off
fuel/air supply.
Note :
•
Practical best(optimum) needle-valve setting
Exhaust note starts to change.
Disconnect battery
leads from glowplug at
about this point.
Clear, high-pitched two-stroke
exhaust note
Maximum rpm
setting("Lean").
STARTING
"Rich" needle-valve
setting when starting
the engine.
The engine may stop if
the battery leads are
disconnected from the
glowplug while the
engine is running rich.
Engine
stops
R
e
v
o
lu
ti
o
n
s
s
ta
rt
t
to
d
e
c
re
a
s
e
.
to
d
e
6
7
1
2
5
4
3
Intermittent, high-pitched
two-stroke note
superimposed
on low "four-stroke"
sound.
Note: Although this is a two-stroke engine it fires like a
four-stroke at these rich needle-valve settings-i.e. ignition
of the fuel charge takes place at every fourth stroke of the
piston instead of at every second stroke.
17