Leakage Test; Preparations - Stihl MS 661 Manual

2
3
– Clean the sealing face.
– Fit a new gasket between the
muffler and exhaust casing.
: Fit the exhaust casing (1), insert
the screws (2, 3) and tighten
them down firmly.
6.2

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 may affect the idle speed in
particular.
Moreover, the transition from idle
speed to part or full throttle may not
be smooth.
Always perform the vacuum test
first and then the pressure test.
The engine can be checked
thoroughly for leaks with the pump
0000 850 1300.
MS 661, MS 661 C-M
6.2.1

Preparations

– Remove the filter cover
2
– Remove the shroud, b 6.4
1
3
The spark plug (1) must be
tightened down firmly.
– Remove the decompression
valve, b 6.9
: Fit the plug (2) 1122 025 2200
and tighten it down firmly.
– Remove the exhaust casing and
loosen the muffler screws, b 6.1
: Fit the sealing plate (1)
0000 855 8106 on the exhaust
port – between the gasket / heat
shield and cylinder.
– Tighten the screws moderately.
The sealing plate must completely
fill the space between the two
screws.
2
1
1
– Remove the carburetor, b 13.4
1
: Washer (1) and sleeve (2) must
be in place.
2
4
3
1
: Coat screw (1) or inside of
impulse hose with STIHL press
fluid, b 16
: Take screw (1) out of flange (2)
and insert it in the impulse
hose (3).
: Push the flange (2)
5910 850 4200 over the collar
screws as far as stop.
: Fit the nuts (4) and tighten them
down firmly.
2
4
25