Adjustment Of Carburetor; Fuel System - Husqvarna 181 Workshop Manual

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Fuel system
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When properly adjusted the lever of the needle valve shall be on a level with the
carburetor housing surrounding it.
If the lever is located too high, the carburetor will be very sensitive as regards
the adjustment of the adjusting needles,
A too low lever induces bad acceleration qualities.
Check that the lever can move freely.
Make a pressure test of the carburetor. Proceed as mentioned above,
Then mount gasket, metering diaphragm and cover.
NOTE!
Care should be taken to ensure that the centre pin of the diaphragm
enters the fork in the lever!
Install the adjusting needles and screw them out to the following basic posi-
tion: H = 1.0 turn open. L = 1.0 turn open.
Adjustmentof carburetor
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Before adjusting the carburetor, proceed as follows:
. Clean the air filter or, if necessary, replace it with a new one.
. Check the spark plug and its electrodes.
. Check that the fuel filter is not clogged.
Examine the fuel filter as follows:
Loosen the fuel hose from the carburetor and lay the chain saw on the clutch
side. Open the tank cap, If there is enough fuel in the tank, some of it now
ought to run out of the hose.
After having made the abovementioned checks you make a basic adjustment of
the carburetor needles, i.e. H = 1 turn open and L = 1 turn open.
Start the chain saw and warm it
u
by applying full throttle and letting it
cut into a log.
A constant speed for 10–20 sec indicates not only a good high speed function
of the carburetor but also a good condition overall.
Should there be a sudden lean suPPly to the engine after approx. 10–20 sec
full throttle running (big speed increase), this would indicate some fault in the
fuel system.
The trouble may be caused by:
. Leakage in the pumping section of the carburetor.
. Crack in the insulating piece.
. Loose carburetor bolts.
. Incorrectly assembled or leaking gaskets.
. Tank breather valve inoperative.
. Fuel filter clogged.
NOTE!
Too lean adjustment of the carburetor would cause a considerable loss
of power. Adjust the carburetor in order to obtain maximum power and
not maximum speed.
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