Decompression Valve - Husqvarna K770 Workshop Manual

6.6.18 High and low speed jets
The low and high speed nozzles on the carburetor have
been factory set. They must not be adjusted.
6.6.19 To adjust the idle speed
The idle speed must be examined during service. Use a
special screwdriver and tachometer. See
overview on page 14 . The cutting blade must be
attached.
The tachometer is induction sensing. It must not be
connected directly to the ignition lead. The air filter cover
must not be removed. The antenna cable supplied with
the tachometer is not usually used.
WARNING: The exhaust fumes are poisonous.
Adjust the idle speed outdoors.
1. Run the machine warm for approximately 5 minutes.
2. Keep the instrument with the arrow pointing down to
the position of the spark plug.
44 - Repair and servicing
3. Adjust the idle screw to an idle speed of
approximately 2,700 rpm.
If the cutting blade rotates at this speed, the clutch or
the friction retarder must be examined.
6.6.20 To assemble the air valve
1. Attach the air valve to the carburetor with 2 screws.
Servicing tools

6.7 Decompression valve

6.7.1 Function
The decompression valve decreases the compression in
the cylinder when the engine is started. A small quantity
of fuel/air mixture goes through the decompression
valve, as shown in figure 1. When the engine fires the
701 - 002 -