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3. Tighten the hose clamp. Make sure that the filter
cannot move off the tube.
7.7 Carburetor
7.7.1 Carburetor structure
6
1
8
9
17
6
16
1. Fuel pump system
2. Primer bulb
3. Idle position
4. Throttle control system
5. High speed position
6. Main nozzle
7. Check valve
8. Outlet tube
9. Inlet tube
10. Air intake
11. Throttle valve
12. Pump chamber
13. Pump diaphragm
14. Pump body
15. Pump cover
16. Pulse hole
17. Metering chamber
18 - Repair instructions
4
12
13
5
14
7
15
2
10
11
11
2
7.7.2 The function of the carburetor
Carburetor structure on page 18 for the
Refer to
illustration for this text.
Before the engine is started, the air in the carburetor
must be removed. When the primer bulb (2) is pushed, a
vacuum is caused in the inner bulb. When the vacuum is
released, fuel moves from the fuel tank through the inlet
tube (9). The fuel continues through the carburetor to
the outlet tube (8) and into the fuel tank. This removes
the air from the carburetor.
3
The fuel pump system (1) has 4 parts, the pump cover
(15), the pump diaphragm (14), the pump body (14) and
the pump chamber (13). When the engine operates, the
fuel pump system supplies fuel to the carburetor. The
crankcase sends a pulse through the pulse hole (15) to
the carburetor. The pulse causes the pump diaphragm
to move up and down in the pump chamber. This
movement causes the fuel to move into the carburetor
chambers.
When the crankshaft rotates, a pressure variation in the
piston makes the pump diaphragm move up and down.
If the pressure is negative, the fuel moves through the
valves from the fuel tank into the fuel chamber. If the
pressure is positive, the fuel in the fuel chamber moves
into the balance fuel chamber.
The throttle cable for the throttle lever is installed on the
throttle control system (4) of the carburetor. When the
throttle lever is pushed, the speed is increased or
decreased. The speed controls the position of the
throttle valve.
When the engine operates at idle speed, the throttle
valve (11) is in the idle position (3). The idle position
means that the throttle valve of the carburetor is not fully
closed. When the engine does not operate at full speed,
the throttle valve is in the part throttle position. The part
throttle position means that the throttle valve of the
carburetor is not fully open. When the engine operates
at high speed, the throttle valve is in the high speed
position (5). The high speed position means that the
throttle valve is fully open.
Air enters the carburetor through the air intake (10). A
fully open throttle valve lets the most air in, and fuel
goes through the main nozzle from the carburetor. The
fuel and the air is mixed into a gas in the venturi. The
mixed gas then moves into the engine.
1296 - 001 - 27.09.2019
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