GEN
INFO
General information
1-17
60C5D11
Acceleration pump
The function of the acceleration pump is to ensure a smooth acceleration by preventing the air-fuel
mixture from becoming temporarily lean in case the throttle valve is opened suddenly. When the
throttle valve is opened suddenly, a large volume of air is introduced into the engine. However,
because fuel is heavier than air, it is not possible to supply the volume of fuel that is necessary for
the large volume of air that has been introduced. Thus, because it is not possible to achieve the air-
fuel mixture that is required by the engine, bucking or hesitation results. For this reason, the acceler-
ation pump temporarily increases the fuel volume in order to adjust the air-fuel mixture to a ratio that
is necessary for the engine in case the throttle valve is opened suddenly.
Operation
When the throttle is opened suddenly, diaphragm (via the link that is connected to the throttle lever)
operates to pressurize the air in the dashpot. The pressurized air distributed to the carburetors by
passing through the in-line, one-way valve that is connected to the carburetors. The pressurized
and distributed air then utilizes the passage of the main air jet to flow into the main nozzle. The pres-
sure of the air helps suck fuel from the main jet, which increases the fuel in the main nozzle, and
thus achieves fuel enrichment.
1
Throttle lever link rod
2
Diaphragm
3
In-line, one-way valve
4
To carburetor #1
5
To carburetor #2
6
To carburetor #3
7
Main jet
8
Carburetor #4 (cutaway view)
9
Dashpot
0
Throttle lever
A
Carburetor #4 (side view)
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