Stihl MS 251 Manual

5MS 231, MS 231 C, MS 251, MS 251 C
2. Specifications
2.1 Engine
MS 231 MS 251
Displacement: 40.6 cm
3
45.6 cm
3
Bore: 41.5 mm 44.0 mm
Stroke: 30.0 mm 30.0 mm
Engine power to ISO 7293: 2.0 kW (2.7 bhp)
at 9,500 rpm
2.2 kW (3.0 bhp)
at 9,500 rpm
Maximum permissible engine speed
with bar and chain: 13,000 rpm 13,000 rpm
Idle speed: 2,800 rpm 2,800 rpm
Clutch: Centrifugal clutch without
linings
Centrifugal clutch without
linings
Clutch engages at: 3,500 rpm 3,500 rpm
Crankcase leakage test
at gauge pressure: 0.5 bar
under vacuum: 0.5 bar
2.2 Fuel System
Carburetor leakage test at
gauge pressure: 0.8 bar
Operation of tank vent at
gauge pressure: 0.5 bar
Fuel: as specified in instruction
manual
2.3 Ignition System
Air gap between ignition
module and fanwheel: 0.30 (+ 0.05/- 0.10) mm
Spark plug (resistor type): NGK CMR 6 H
Electrode gap: 0.5 mm
2.4 Chain Lubrication
Speed-controlled Ematic oil pump
Oil delivery rate: 8.0 (+/3.0) cm
3
/min
at 10,000 rpm
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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