Stihl MS 251 Manual

39MS 231, MS 231 C, MS 251, MS 251 C
: Release the crankshaft (1) from
the bearing seats (arrows) in the
cylinder (2) and pull it out
together with the piston.
: Pull off the oil seals (1)
– always install new oil seals.
: Remove sealant from the sealing
face (arrows) on the engine
pan (1).
– Inspect and clean the sealing
face, b 14
2310RA099 TG
1
2
1
2310RA100 TG
1
2310RA101 TG
1
– Inspect the intake manifold (1)
and replace it if necessary – even
very minor damage can result in
engine running problems, b 3.7
: Take out the screws (2).
: Remove the intake manifold (1).
: Remove sealant and gasket
residue from the sealing
faces (arrows) of the cylinder (1).
– Inspect and clean all sealing
faces, b 14
When reinstalling the cylinder,
always seal it with fresh sealant on
the engine pan.
– Inspect the piston and piston
rings and replace if necessary,
b 6.8, b 6.9
2310RA102 TG
2
2
1
2
2310RA103 TG
1
If the piston or the oil seals are
damaged, also inspect the inside of
the cylinder for signs of damage and
install a new cylinder if necessary.
Installing
: Fit the manifold (1) in position.
: Insert and tighten down the
screws (2) firmly.
Use soft oil seal (1) 9638 003 1581
with snap ring for replacement on
closed engine.
Use hard oil seal (2) 9639 003 951
without snap ring for replacement
on opened engine.
Install the soft oil seal with the snap
ring facing outwards and the hard oil
seal with its open side facing the
ball bearing.
2310RA104 TG
2
2
1
2
2
1
4903RA275 TG
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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