Stihl MS 171 Manual page 30

8.2 Leakage Test
Defective oil seals and gaskets or
cracks in castings are the usual
causes of leaks. Such faults allow
supplementary air to enter the
engine and upset the fuel-air
mixture.
This makes adjustment of the
prescribed idle speed difficult, if not
impossible.
Moreover, the transition from idle
speed to part or full throttle is not
smooth.
Always perform the vacuum test
first.
The engine can be checked
thoroughly for leaks with the pump
0000 850 1300.
8.2.1 Preparations
1
– Remove the shroud, b 8.4
: Unscrew the spark plug (1).
– Set the piston to top dead center.
This can be checked through the
inlet port.
: Fit spark plug (1) and tighten it
down firmly.
– Tightening torques, b 3.5
MS 171, MS 181, MS 211
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: Pry the plugs (arrows) out of the
muffler.
– Take out the screws.
– Remove the muffler.
1
– Fit the flange (1) 1123 855 4200.
: Insert the screws (arrows).
1
: Fit the sealing plate (1)
0000 855 8106 between the
cylinder exhaust port and flange
and tighten down the screws
moderately.
The sealing plate must completely
fill the space between the two
screws.
– Remove the carburetor, b 14.3
1
: Check that the sleeve (1) is in
place.
1
: Fit the test flange 1139 893
2500 (1).
: Fit the nuts (arrows) and tighten
them down firmly.
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