Instruction Manual

MS 660
English
42
It is usually necessary to change the
setting of the idle speed screw (LA) after
every correction to the low speed
screw (L).
Fine Tuning for Operation at High
Altitude
A slight correction of the setting may be
necessary if engine does not run
satisfactorily:
N Carry out the standard setting.
N Warm up the engine.
N Turn the high speed screw (H)
slightly clockwise (leaner). On
carburetors with H = 3/4, turn no
further than stop.
NOTICE
After returning from high altitude, reset
the carburetor to the standard setting.
If the setting is too lean there is a risk of
engine damage due to insufficient
lubrication and overheating.
In some countries, the muffler is fitted
with a spark arresting screen.
N If engine performance deteriorates,
check the spark arresting screen in
the muffler
N Let the muffler cool down
Version A
N Remove four screws
N Remove exhaust casing (1) of the
muffler
N Bend back the retaining lugs (2)
N Pull out spark arresting screen (3)
N Clean the dirty spark arresting
screen, replace if damaged or
heavily carbonized
N Refit the spark arresting screen in
reverse order of steps
Version B
In this version, the muffler is equipped
with two spark arresting screens.
N Remove screw (1)
N Lift and pull out the spark arresting
screen (2)
N Clean the dirty spark arresting
screen, replace if damaged or
heavily carbonized
N Refit the spark arresting screen in
reverse order of steps
N Check second spark arresting
screen – as with Version A
Spark Arresting Screen in
Muffler
137BA025 KN
1
137BA026 KN
3
2
1
178BA010 KN
2