33MS 231, MS 231 C, MS 251, MS 251 C
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 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 and then the pressure test.
The engine can be checked
thoroughly for leaks with the pump
0000 850 1300.
6.2.1 Preparations
– Remove the shroud, b 6.4
– Pull off the boot and unscrew the
spark plug.
– Set the piston to top dead center.
This can be checked through the
spark plug hole.
2310RA079 TG
1
: Fit the spark plug (1) and tighten
it down firmly.
– Remove the muffler and gasket,
b 6.1
: Fit the test flange (1)
5910 855 4201 on cylinder
exhaust port.
: Fit the screws (2)
– do not tighten down yet.
Flange (1) 4224 893 2501 can be
modified as shown.
a = 13 mm
b = 39.25 mm
c=6mm
2
2310RA072 TG
1
2
c
b
2710RA164 TG
a
: Fit the sealing plate (1)
0000 855 8106 between the
cylinder exhaust port and
flange (2).
: Tighten the screws (3)
moderately.
The sealing plate must completely
fill the space between the two
screws.
– Remove the carburetor, b 12.5
: Make sure the washer (1) is in
place.
2
3
2310RA074 TG
1
3
2310RA073 TG
1
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