Stihl MS 251 Manual

81MS 231, MS 231 C, MS 251, MS 251 C
12. Fuel System
12.1 Air Filter
Dirty air filters reduce engine power,
increase fuel consumption and
make starting more difficult. The air
filter should be checked when there
is a noticeable loss of engine power.
– See also Troubleshooting,
b 3.6, b 3.7
– Remove the shroud, b 6.4
: Rotate the air filter (1)
counterclockwise and lift it away.
– Check the air filter and clean or
replace if necessary
– see instruction manual.
– Reassemble in the reverse
sequence.
2310RA312 TG
1
12.2 Baffle
– Remove the air filter, b 12.1
: Unscrew the nuts (arrows).
: Remove the baffle (1).
– Check the baffle and replace it if
necessary
– Reassemble in the reverse
sequence.
12.3 Filter Base
– Remove the air filter, b 12.1
– Remove the choke rod,
b 10.3.3
– Remove the baffle, b 12.2
: Pry the filter base (1) out of the
buffer (2).
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1
2
2310RA195 TG
1
: Pull the filter base (1) off the
studs (arrows).
: Pull the filter base (1) out of the
buffer (2).
: Pull the short circuit wire (1) and
ground wire (2) out of the
guides (arrows).
– Remove the contact spring,
b 7.7.4
– Remove the switch shaft, b 10.1
– Remove the filter base.
2310RA198 TG
1
2
2310RA197 TG
1
2
2310RA196 TG
1
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Stihl MS 251 Specifications

General

Idle speed	2800 RPM
Motor type	2-stroke motor
Chain pitch	1/308 \
Blade length	450 mm
Product color	Black, Grey, Orange
Motor speed (max)	10000 RPM
Oil tank capacity	0.2 L
Fuel tank capacity	0.39 L
Engine displacement	45.6 cm³
Kickback protection	Yes
Engine power	3 hp
Power source	Gasoline
Sound power level	114 dB
Vibration emission	3.9 m/s²
Sound pressure level	103 dB

Weight and Dimensions

Weight	4900 g