Yamaha F4B, Service Manual

Page: 39 / 202

2-10
Fuel system
0
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3
4
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8
9
10
A
Medium speed operation
When running at medium speed, the air that has entered through the main bore
a
flows faster,
causing negative pressure to increase in the main bore
a
.
When the negative pressure in the main bore
a
increases, the fuel is sucked from the main jet
a
to
be mixed with the air that has entered from the main air jet
b
through the emulsion tube
c
, and
then drawn into the main nozzle
b
.
The fuel drawn into the main nozzle
b
is mixed with the air in the venturi, producing air and fuel mix-
ture that will be supplied to the engine.
The air and fuel mixture is simultaneously supplied to the engine through the pilot hole
d
and the
bypass holes
e
.
A
Air
B
Fuel
C
Air and fuel mixture
A
B
C
e
d
b
c
a
b
a