Stihl MS 251 Manual

44 MS 231, MS 231 C, MS 251, MS 251 C
: Apply the installing tool
5910 890 2210 with the sleeve
against the piston boss, hold the
piston steady, center the tool
shank exactly and press home
until the snap ring slips into the
groove.
Make sure the tool is held square on
the piston pin axis.
– Inspect the piston rings and
replace if necessary, b 6.9
– Install the crankshaft and new oil
seals, b 6.5
– Install the crankshaft, b 6.6
– Install the engine, b 6.5
2310RA420 TG2310RA421 TG
6.9 Piston Rings
– Remove the piston, b 6.8
– Remove the piston rings from the
piston.
: Use a piece of old piston ring to
scrape the grooves (arrows)
clean.
: Position the new piston rings so
that the radii face
upward (arrows).
5902RA160 TG5902RA161 TG
– Carefully fit the piston rings over
the piston
– they might otherwise break.
: Install the piston rings so that the
radii at the ring gap meet at the
fixing pins in the piston
grooves (arrows).
: Check correct installed position
of the piston rings (arrows).
– Install the piston, b 6.8
– Reassemble all other parts in the
reverse sequence.
5902RA162 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