74 MS 440, MS 440 C
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!
In the event of trouble with the
carburetor or the fuel supply
system, always check and clean the
tank vent.
Check function by performing
vacuum test on the tank via the fuel
hose.
– Remove the carburetor –
b 12.2.1
: Connect service tool (1)
0000 850 3501 to the fuel hose
and create a vacuum in the fuel
tank.
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: Equalization of pressure takes
place via the tank vent (1). There
must not be any build-up of
vacuum in the tank. In the event
of a malfunction, pry out the tank
vent with a slotted screwdriver
and fit a new valve with new
O-ring.
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The diaphragm pump draws fuel
from the tank into the carburetor
through the fuel hose. Any
impurities mixed with the fuel are
retained by the pickup body. The
fine pores of the filter eventually
become clogged with minute
particles of dirt. This restricts the
passage of fuel and results in fuel
starvation.
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
: Remove the fuel tank cap and
drain the tank.
– Pour a small amount of clean
gasoline into the tank. Close the
tank and shake the saw
vigorously.
– Open the tank again and drain it.
Dispose of fuel properly in
accordance with environmental
requirements!
Pickup body
: Use hook (1) 5910 893 8800 to
pull the pickup body out of the
fuel tank.
Do not stretch the fuel hose too
much during this operation.
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12.5 Tank Vent 12.6 Pickup Body
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