Stihl MS 251 Manual

91MS 231, MS 231 C, MS 251, MS 251 C
: Take out the screw (1).
: Remove the inlet control lever (2)
with
spindle (3) out of the inlet
needle’s groove.
The small spring under the inlet
control lever may pop out.
: Remove the inlet needle (1).
: Remove the spring (2). Inspect
and replace if necessary.
: If there is an annular
indentation (arrow) on the
sealing cone of the inlet needle,
fit a new inlet needle.
2310RA261 TG
3
1
2
2310RA262 TG
1
2
165RA348 TG
Installing
: Fit the inlet needle (1).
: Fit the spring (2) in the bore.
: Position the inlet control lever (3)
with spindle (2) on the
spring (arrow) first, then slide the
inlet control lever’s clevis into the
groove in the inlet needle (1).
Make sure the spring locates on the
control lever’s nipple.
– Press the inlet control lever down
and secure it with the screw.
– Check that the inlet control lever
moves freely.
– Install the metering diaphragm,
b 12.6.1
2310RA263 TG
1
2
2310RA264 TG
1
2 3
12.6.3 Pump Diaphragm
– Troubleshooting, b 3.6
– Remove the carburetor, b 12.5
: Take out the screw (1).
: Remove the end cover (2).
If the gasket and pump diaphragm
are stuck to the carburetor, remove
them very carefully.
2310RA265 TG
1
2
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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