Tank Vent; Pickup Body - Stihl FS 25-4 User Manual

11.3

Tank Vent

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.
Important: If problems occur on
the carburetor or the fuel supply
system, always check and clean
the tank vent.
Check function by performing
pressure and vacuum tests on
the tank via the fuel hose.
Equalization of pressure from the
outside inwards takes place via
the thread in the filler cap, the val-
ve and holes in the cap.
Equalization of pressure from the
inside outwards takes place via
the holes in the cap, the slots in
the valve body and thread in the fil-
ler cap.
FS 25-4, 65-4
Cleaning
- Unscrew the filler cap.
•
Ease the cap (1) off the valve
body (2).
•
Take the cap (3) out of the valve
body.
•
Remove sealing ring (4) from the
valve body.
- If the sealing ring is damaged, fit
a new fuel filler cap (5).
•
Wash valve body and valve (6)
in fresh gasoline.
- If the valve is damaged, fit a new
fuel filler cap.
•
Insert cap (3) in the valve body.
•
Slip sealing ring (4) over the val-
ve body.
•
Fit cap (1) on valve body and
push it home until it snaps into
position.
- Screw on the fuel filler cap.
11.4

Pickup Body

The diaphragm pump draws fuel
out of the tank and into the
carburetor via the fuel hose. Any
impurities mixed with the fuel are
retained by the pickup body (filter).
The fine pores of the filter event-
ually become clogged with minute
particles of dirt. This restricts the
passage of fuel and results in fuel
starvation.
Important: In the event of trouble
with the fuel supply system,
always check the fuel tank and
the pickup body first. Clean the
fuel tank if necessary.
Cleaning the fuel tank
- Unscrew the filler cap and drain
the tank.
- Pour a small amount of clean
gasoline into the tank.
- Close the tank and shake the
unit vigorously.
- Open the tank again and drain it.
Note: Dispose of fuel properly.
Pickup body
- Unscrew the filler cap and
remove it together with the
retainer.
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