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 many
tries to start, 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. Increase the pressure to
approximately 30 psi/2 bar. Let the fuel go out through
the venturi which is fully in water. Not until air bubbles
come from the venturi, can the function of the needle
valve be examined as set out below.
6.6.8.3 To examine external leakage and the function of
the needle valve
1. Lower the carburetor into water.
2. Connect a piece of hose to the pulse line. It must
come out above the water line.
3. Connect the pressure tester to the fuel line.
4. Increase the pressure to 15–36 psi/100–2.5 bar.
The needle valve must lift and air bubbles come out of
the jets in the venturi. The pressure must then decrease
to approximately 15–7 psi/100–0.5 bar and then
decrease much slower or stop. A pressure drop after 7
psi/0.5 bar means there is a leak at the needle valve. If
the needle valve does not open at 36 psi/2.50 bar (max.
permitted pressure test), blow through the hole for filter
compensation (A) to open it. If the pressure does not
1453 - 001 - 02.04.2020
Repair and servicing - 37
Summary of Contents for K770 SmartGuard
Page 1: ...Workshop manual K770 SmartGuard English 1453 001 02 04 2020 ...
Page 6: ...3 2 Tightening torques 3 5 4 6 4 6 4 6 2 0 7 9 3 5 4 6 6 Servicing data 1453 001 02 04 2020 ...
Page 7: ...11 12 10 12 5 7 11 13 11 13 11 13 7 9 17 23 1453 001 02 04 2020 Servicing data 7 ...
Page 9: ...13 6 8 20 25 5 5 6 10 12 6 6 4 3 5 7 5 6 8 25 30 9 11 1453 001 02 04 2020 Servicing data 9 ...
Page 74: ...74 Wiring diagram 1453 001 02 04 2020 ...
Page 75: ...1453 001 02 04 2020 Wiring diagram 75 ...
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