Stihl MS 251 Instruction Manual - Page 97

Standard setting, counterclockwise until the chain

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1 This completes the basic setting of the high speed screw H and the low speed screw L . The setting of the high speed screw H is fixed when the limiter cap (1) is flush with the carburetor body. 12.7.2 Standard setting The limiter cap must not be removed for the standard setting. Always perform the following steps before carrying out any adjustments: - Troubleshooting, b 3.6 - Check chain tension and adjust if necessary. - Inspect the spark arresting screen (if fitted) and clean or replace if necessary, b 3.7 or b 6.1 2310RA285 TG - Check the air filter and clean or replace if necessary, b 12.1 Standard setting - Shut off the engine. - Turn the high speed screw (H) slowly counterclockwise as far as stop, but not more than a 3/4 turn. - Turn the low speed screw (L) slowly clockwise as far as stop, then turn it back 1 full turn. Check running behavior: The engine must idle and accelerate smoothly. Adjusting engine idle speed - Carry out standard setting. - Warm up the engine. Engine stops while idling - Turn the idle speed screw (LA) clockwise until the chain starts running, then turn it back 1 full turn. Saw chain runs while engine is idling - Turn the idle speed screw (LA) counterclockwise until the chain stops running, then turn it back 1 full turn. Erratic idling behavior, poor acceleration (although standard setting is correct) Idle setting too lean. - Warm up the engine. - Turn low speed screw (L) counterclockwise 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). Adjustment for operation at high altitude A minor correction may be necessary if engine power is not satisfactory when operating at high altitude. - Check standard setting. - Warm up the engine. - Turn the high speed screw (H) clockwise (leaner) - no further than stop. Turn the adjusting screws only very slightly. Even minor adjustments can noticeably affect engine running behavior. If the setting is made too lean there is a risk of engine damage as a result of lack of lubrication and overheating. 96 MS 231, MS 231 C, MS 251, MS 251 C

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96
MS 231, MS 231 C, MS 251, MS 251 C
This completes the basic setting of
the high speed screw
H
and the low
speed screw
L
.
The setting of the high speed
screw
H
is fixed when the limiter
cap (1) is flush with the carburetor
body.
12.7.2
Standard setting
The limiter cap must not be
removed for the standard setting.
Always perform the following steps
before carrying out any
adjustments:
– Troubleshooting,
b
3.6
–
Check chain tension and adjust if
necessary.
–
Inspect the spark arresting
screen (if fitted) and clean or
replace if necessary,
b
3.7 or
b
6.1
2310RA285 TG
1
–
Check the air filter and clean or
replace if necessary,
b
12.1
Standard setting
–
Shut off the engine.
–
Turn the high speed screw (
H
)
slowly counterclockwise as far as
stop, but not more than
a 3/4 turn.
–
Turn the low speed screw (
L
)
slowly clockwise as far as stop,
then turn it back
1 full turn.
Check running behavior:
The engine must idle and
accelerate smoothly.
Adjusting engine idle speed
–
Carry out standard setting.
–
Warm up the engine.
Engine stops while idling
–
Turn the idle speed screw (
LA
)
clockwise until the chain starts
running, then turn it back 1 full
turn.
Saw chain runs while engine is
idling
–
Turn the idle speed screw (
LA
)
counterclockwise until the chain
stops running, then turn it back
1 full turn.
Erratic idling behavior, poor
acceleration
(although standard setting is
correct)
Idle setting too lean.
–
Warm up the engine.
–
Turn low speed screw (
L
)
counterclockwise 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
).
Adjustment for operation at high
altitude
A minor correction may be
necessary if engine power is not
satisfactory when operating at high
altitude.
–
Check standard setting.
–
Warm up the engine.
–
Turn the high speed screw (
H
)
clockwise (leaner) – no further
than stop.
Turn the adjusting screws only very
slightly. Even minor adjustments
can noticeably affect engine running
behavior.
If the setting is made too lean there
is a risk of engine damage as a
result of lack of lubrication and
overheating.