Stihl MS 650

74 MS 650, MS 660
In the case of problems with the
carburetor or fuel supply system,
also check and clean the tank vent –
b 12.6.
The carburetor can be tested for
leaks with the carburetor and
crankcase tester 1106 850 2905.
– Remove the carburetor –
b 12.2.1
: Push the fuel line (1)
1110 141 8600 onto the
nipple (2) 0000 855 9200.
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: Push the fuel line with nipple onto
the carburetor’s elbow connector.
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: Push the nipple into the pressure
hose of tester 1106 850 2905.
: Close the vent screw (1) on the
rubber bulb (2) and pump air into
the carburetor until the pressure
gauge (3) shows a reading of
approx. 0.8 bar (80 kPa).
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If this pressure remains constant,
the carburetor is airtight. However, if
it drops, there are two possible
causes:
1. The inlet needle is not sealing
(foreign matter in valve seat or
sealing cone of inlet needle is
damaged or inlet control lever
sticking). Remove to clean –
b 12.3.2
2. Metering diaphragm damaged,
replace if necessary – b 12.3.1
– After completing the test, open
the vent screw (1) and pull the
fuel line off the carburetor.
– Install the carburetor – b 12.2.1
– Push the fuel hose onto the
elbow connector.
Reassemble all other parts in the
reverse sequence.
– Remove the carburetor –
b 12.2.1
– Remove sleeve from end cover.
: Take out the screws (1).
: Remove the end cover (2).
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: Remove the metering diaphragm
and gasket from the carburetor or
end cover.
: Carefully separate the diaphragm
and gasket.
– Inspect diaphragm for damage
and wear and replace if
necessary.
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12.2.2 Leakage Test 12.3 Servicing the Carburetor
12.3.1 Metering Diaphragm