Servicing The Carburetor; Metering Diaphragm - Stihl MS 261 User Manual

: Push the fuel hose with nipple
onto the carburetor's fuel
stub (arrow).
2
1
– Push the pressure hose of pump
0000 850 1300 onto the nipple.
: Push the ring (1) to the right and
pump air into the carburetor until
the pressure gauge (2) indicates
a pressure of about
0.8 bar (80 kPa).
If this pressure remains constant,
the carburetor is airtight. However, if
it drops, there are three possible
causes:
1. The inlet needle is not sealing
(foreign matter in valve seat,
sealing cone of inlet needle
is damaged or
inlet control lever is sticking),
remove to clean,
b 12.6.2 or b 12.6.2
2. Metering diaphragm or gasket
damaged, replace if necessary,
b 12.6.1 or b 12.10.1
112
3. Pump diaphragm or
gasket damaged, replace
if necessary, b b 12.6.3 or
b 12.10.1
– After completing the test, push
the ring (1) to the left to vent the
system and then pull the fuel
hose off the carburetor.
– Install the filter base, b 12.3
– Reassemble all other parts in the
reverse sequence.
12.6

Servicing the Carburetor

12.6.1 Metering Diaphragm

– Troubleshooting, b 3.6
– Remove the carburetor, b 12.5
: Take out the screws (arrows).
: Remove the end cover (1).
If the gasket and diaphragm are
stuck to the carburetor, remove
them very carefully.
2 1
: Carefully separate the metering
diaphragm (1) and gasket (2).
The diaphragm material is
subjected to continuous alternating
stresses and eventually shows
signs of fatigue. i.e. the diaphragm
distorts and swells and has to be
replaced.
– Check the metering diaphragm
for signs of damage and wear.
Install a new gasket.
Installing
1
2
1
– Note installed positions of
metering diaphragm (2) and
gasket (1).
: Position the gasket (1) and
metering diaphragm (2) so that
the holes (arrows) are in line with
the recess (3).
MS 261, MS 261 C
3