Stihl 4180 Series - Tank Vent; Checking Operation

27Series 4180 Powerhead
All models
: Place the new limiter caps on the
screws (1 and 2) so they are
positioned against the rich stop
(arrow)
VA
249RA166
2
1
: Push limiter caps onto the screws
to the second noticeable stop
(until dimension “a” is 5 mm).
Limiter caps must not butt against
the carburetor body.
– Adjust engine idle speed, b
6.4
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Correct operation of the carburetor
is only possible if atmospheric
pressure and internal fuel tank
pressure are equal at all times. This
is ensured by the tank vent.
In the case of problems with the
carburetor or fuel supply system,
also check the tank vent.
There are two types of tank vents:
: Tank vent (A) without return line.
: Tank vent (B) with connection to
return line on the clean air side of
the air filter.
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AB
: Only tank vent (A) without return
line may be installed in fuel tanks
with a 2.2 mm shoulder (a).
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: A tank vent with return line (B)
may be installed or retrofitted in
fuel tanks with a 5.2 mm shoulder
(a).
Check function of tank vent by
carrying out vacuum test on fuel
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tank via the fuel hoses.
To do this:
– Drain the fuel tank, b
6.6.1
: Pull both fuel hoses (1 and 2) off
the carburetor.
– Use a suitable plug to seal the
fuel hose (1).
VA
249RA013
2
1
6.5 Tank Vent
6.5.1 Checking Operation