Technical Information · issue 22 of 1995
Decompression valve; filter cover
Model 066 chain saws from machine number
Part changes (1)
| Was | Becomes | What the bulletin says |
|---|---|---|
| 1122 140 1000 | 1122 140 1001 | 2.=Filter cover=fn the future, filter cover 1122 140 1000 will be replaced by filter cover 1122 140 1001 on all HD filter versions. |
Full text
Page 1 of 3
Technical Information
22.95
Model 066 Chain Saws - Series 1122
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1. All versions with decompression valve
2. Filter cover
1.=All versions with decompression
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Model 066 chain saws from machine number
X 32 231 689 will come with a GHFRPSUHVVLRQ
YDOYH.
The decompression valve releases the compres-
sion pressure in the combustion chamber during
starts and thus reduces the effort required to pull
the starter rope.
The valve is opened manually and closes
automatically as soon as the engine begins to fire.
137TI008
Construction and method of operation
The main components of the decompression valve
are the body (1) and plunger (2). 3
The plunger moves axially in the valve body.
The bottom end of the plunger is cone-shaped. 1
Three spring-loaded balls (3), each offset 120°,
hold the plunger in its upper or lower position.
The complete valve is screwed into the cylinder.
2
137TI006 KN
)Technical Information 22.95 - Page 2
Before starting, the plunger (2) is pushed into its
lower position. The cone moves away from the
body (1), the decompression valve is open.
The crankshaft is rotated via the rewind starter.
The upward stroke of the piston causes the 3
mixture in the cylinder to be compressed. A small 1
amount of the gas in the cylinder is pushed out
through the bore in the valve body (see arrow).
The remaining gas in the cylinder is compressed
but the resulting pressure is lower than the 2
decompression valve’s closing pressure.
137TI007 KN
Only after the combustible mixture is ignited does
the pressure in the cylinder exceed the decom-
pression valve’s closing pressure.
The plunger (2) is then pushed upwards and
the cone closes the bore.
The shroud now has an opening to accommodate
the decompression valve.
The area around the opening is raised (see arrow)
to protect the decompression valve from
accidental contact.
137TI011 S
A cover 1122 084 1405 is fitted between the
cylinder and shroud to help prevent the entry
of dust and dirt.
137TI010 S
Service note
Only the new shroud is available as a replacement.
If it is used for a machine without decompression
valve, the opening must be sealed with the cap
1122 084 7100 provided.
The decompression valve can be removed and
installed with a standard commercial long-reach
13-mm socket. Tightening torque 14 Nm (10.3
lbf.ft).
To carry out the pressure test on the engine, we
137TI009 S
recommend that the decompression valve be
removed and the tapped hole sealed with the plug
1122 025 2200.
)Technical Information 22.95 - Page 3
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Part Name Original New Key Rem. MOQ
version version H
Cylinder with piston;
including item 2: 1122 020 1208 1122 020 1210 1 1) 1
Plug
Decompression valve --- 1122 025 2200 2 5
Cover --- 1128 020 9400 3 1
Shroud; --- 1122 084 1405 4
including item 6: 1122 080 1605 1122 080 1606 5 1) 1
Cap
All other parts as before --- 1122 084 7100 6 1
Modification to be introduced from machine number X 32 231 689
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1) Original version of part will be supplied from factory only as long as existing stocks last
2.=Filter cover
In the future, filter cover 1122 140 1000 will be
replaced by filter cover 1122 140 1001 on all HD
filter versions. This change has been made in
connection with modifications to Magnum models.
The sides of the new version has been extended
forward to close the gap between the carburetor
box and the filter cover.
137TI005
A B
A = Original version
B = New version
Last Technical Information on model 066: 10.95
for USA : 19.95
Waiblingen, March 30, 1995 Andreas Stihl - D1/MTK-al
1995 Andreas Stihl Technical Documentation Page 2 of 3
Page 3 of 3
Extracted from the manufacturer's 2012 service catalogue. Most of these PDFs embed fonts with a shifted character map, so the text above was recovered rather than copied — read it as a faithful but imperfect transcription, and treat the page image above each block as the authority where the two disagree — the figures exist only there, because they are vector drawings that text extraction cannot keep.