Husqvarna K770 Workshop Manual page 39

5. Fuel line
6. Connection to air purge
7. High and low speed jet (set at the factory)
8. Idle screw, speed adjustment
9. Throttle rod for the choke
10. SmartCarb
11. Pump diaphragm – on top in relation to the
crankcase through the pulse line – fuel below the
diaphragm
12. Valves of the fuel pump
13. Fuel chamber, measurement chamber diaphragm
above
14. Needle valve for pressure regulator
6.6.6 Pressure tester
The pump piston of the pressure tester (refer to
Servicing tools overview on page 13 ) must be operated
with one hand. The pressure tester is supplied with an
adapter for small dimensions. Make the hose connection
as short as possible, this gives a more accurate test
result.
701 - 002 -
6.6.7 To remove the air valve
It is not necessary to remove the air valve to do
servicing on the carburetor, but it makes it easier.
1. Make a note of the connection of the link rod.
2. Remove the 2 screws.
6.6.8 Needle valve
6.6.8.1 Indications of a needle valve leak
There are many symptoms of a needle valve with a leak.
A product that is used for short periods is usually not
easy to start when it is warm. Fuel leaks into the venturi
and gives too much fuel for the next warm start.
With a cold start, the fuel chamber above the needle
valve is dry. This is the situation especially when the
product has not been used for a long period. After trying
to start many times, new fuel has gone into the
carburetor and the product starts.
6.6.8.2 Test conditions
The best test result is from a carburetor that is drained,
but has some fuel left. Do not examine a fully dry
carburetor, or a carburetor that has not been used for a
long time. The result will not be accurate. When the
carburetor is full, turn the carburetor with the pulse line
up, as shown in the picture. Pump up the pressure to
approximately 30 psi/2 bar. Let the fuel run out through
the venturi which is fully in water. Not until air bubbles
Repair and servicing - 39