Technical Information · issue 55 of 2002

Decompression Valve, Cylinder with Piston, Cover, Summary

Model MS 360 Chainsaw – Series 1125

IssueTI 55/2002

Engine family 1125

Part changes (1)

Was	Becomes	What the bulletin says
1125 020 1206	1125 020 1215	Cover The previous cylinder with piston 1125 020 1206 will be replaced by version 1125 020 1215.

Full text

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Technical Information

55.2002
Model MS 360 Chainsaw – Series 1125

Contents
1. Decompression Valve
2. Cylinder with Piston

3. Cover

4. Summary

1. Decompression Valve
The STIHL MS 360 will come standard with a The plunger (2) is pushed into the lower position

decompression valve in future. before starting. This lifts the cone off the body (1)
The decompression valve reduces the compression and opens the decompression valve. The engine is
pressure in the combustion chamber during starting
and improves starting convenience.
cranked by way of the rewind starter. The resultant
build-up of pressure in the cylinder causes a certain
amount of gas to escape through the bore (see
This reduces the physical effort required to pull the
arrow).
starter rope. The decompression valve is opened
The remaining gas in the cylinder is compressed,
manually and closes automatically as soon as the

but the pressure that occurs during this process is
engine fires.
lower than the decompression valve’s closing
pressure.
1.1 Construction and Function
The pressure in the cylinder exceeds the

decompression valve’s closing pressure as soon as

the combustible mixture is ignited.
3
This causes the plunger (2) to be pushed upwards
1 and the cone then seals the bore again.

1.2 Service Notes

2 The decompression valve can be removed and
installed with a standard long-reach 13 mm socket.
137TI007 KN

The tightening torque is 14 Nm.
To perform the engine leakage test, remove the

decompression valve and seal the hole with plug
The main parts of the decompression valve are the 1122 025 2200.

body (1) and plunger (2). To avoid damaging the decompression valve during
The plunger moves axially inside the valve body. Its servicing work, make sure it is closed before fitting
bottom end is cone-shaped. Three spring-loaded the locking strip to block the piston.
balls (3), each offset 120°, hold the plunger in the
upper or lower position. The decompression valve is
screwed into the cylinder.

TI_55_2002_01_01_01.fm englisch / english
)m~ge 2 Technical Information 55.2002

2. Cylinder with Piston 3. Cover
The previous cylinder with piston 1125 020 1206 will
be replaced by version 1125 020 1215.
Parts availability
Only the new cylinder with piston 1125 020 1215 is
available as a replacement. On machines without a
decompression valve it is necessary to seal the hole
in the cylinder for the decompression valve with the
plug 1122 025 2200 which is included in the scope
of supply.

176TI012 KN
Cover 1122 084 1405 is fitted between the cylinder

and shroud to prevent the ingress of dirt.

4. Summary
Item Part Name Previous
fo New Remarks
1 Cylinder with piston; 1125 020 1206 --- 1)
2 Cylinder with piston; --- 1125 020 1215
including item 3:

3 Plug --- 1122 025 2200
4 Decompression valve --- 1128 020 9400
5 Cover --- 1122 084 1405

Modification to be introduced: in progress

Remarks
1) Previous version of part will be supplied from factory only as long as existing stocks last

Last Technical Information on model MS 360: 31.2001

TI_55_2002_01_01_01.fm

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