Stihl MM 55 Instruction Manual - Page 22

Spark Plug

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000BA039 KN English Erratic idling behavior, poor acceleration (despite correction to setting of LA screw). Idle setting is too lean N Turn the low speed screw (L) carefully counterclockwise, no further than stop, until the engine runs smoothly and accelerates well. Erratic idling behavior Idle setting is too rich N Turn the low speed screw (L) slowly clockwise until the engine runs and accelerates smoothly. 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 the engine does not run satisfactorily: N Carry out the standard setting. N Warm up the engine. N Turn high speed screw (H) slightly clockwise (leaner) - 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. Spark Plug If the engine is down on power, difficult to start or runs poorly at idling speed, first check the spark plug. Install a new spark plug after approx. 100 operating hours or earlier if the electrodes are badly eroded/corroded. The wrong fuel mix (too much engine oil in the gasoline), a dirty air filter and unfavorable running conditions (mostly at part throttle etc.) affect the condition of the spark plug. These factors cause deposits to form on the insulator nose which may degrade performance. Remove the spark plug N Move the slide control to STOP-0 1 N Unplug spark plug boot (1) N Unscrew spark plug 232BA081 KN Checking the spark plug A N Clean the spark plug if it is dirty N Check the electrode gap (A) and readjust if necessary - see "Specifications" N Use only resistor type spark plugs of the approved range Correct the problems that have caused fouling of the spark plug: - too much oil in fuel mix, - dirty air filter, - unfavorable running conditions, e.g. operating at part throttle. 20 MM 55, MM 55 C

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MM 55, MM 55 C
English
20
Erratic idling behavior, poor acceleration
(despite correction to setting of LA
screw).
Idle setting is too lean
N
Turn the low speed screw (L)
carefully counterclockwise, no
further than stop, until the engine
runs smoothly and accelerates well.
Erratic idling behavior
Idle setting is too rich
N
Turn the low speed screw
(L) slowly
clockwise until the engine runs and
accelerates smoothly.
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 the engine does not run
satisfactorily:
N
Carry out the standard setting.
N
Warm up the engine.
N
Turn high speed screw (H) slightly
clockwise (leaner) – 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.
If the engine is down on power, difficult
to start or runs poorly at idling speed,
first check the spark plug.
Install a new spark plug after approx.
100 operating hours or earlier if the
electrodes are badly eroded/corroded.
The wrong fuel mix (too much engine oil
in the gasoline), a dirty air filter and
unfavorable running conditions (mostly
at part throttle etc.) affect the condition
of the spark plug. These factors cause
deposits to form on the insulator nose
which may degrade performance.
Remove the spark plug
N
Move the slide control to
STOP-0
N
Unplug spark plug boot (1)
N
Unscrew spark plug
Checking the spark plug
N
Clean the spark plug if it is dirty
N
Check the electrode gap (A) and
readjust if necessary – see
"Specifications"
N
Use only resistor type spark plugs of
the approved range
Correct the problems that have caused
fouling of the spark plug:
–
too much oil in fuel mix,
–
dirty air filter,
–
unfavorable running conditions, e.g.
operating at part throttle.
Spark Plug
1
232BA081 KN
000BA039 KN
A