Yamaha F50A Service Manual page 21

Operation
When the throttle is opened suddenly, diaphragm 1 (via the link that is connected to the throttle
lever) operates to pressurize the air in the pump chamber. The pressurized air opens diaphragm 2,
and becomes distributed to the carburetors by passing through the pipes that are 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 pressure of the air helps suck fuel from the main jet, which increases the
fuel in the main nozzle, and thus achieves the fuel enrichment.
:
:
1 Main air jet
2 Main nozzle
3 Main jet
4 Throttle valve
5 Pilot screw
6 Pilot outlet
7 Pilot jet
8 From acceleration pump
9 Throttle valve closing
0 Throttle valve opening
62Y3A11
1
2
3
9
A
B
1
6
5
4
8
0
A
A Diaphragm 1
B Diaphragm 2
C To carburetors
È Air flow
É Throttle valve opening direction
Technical tips
2
7
3
B
C
S62Y1300
1-16
1
2
3
4
5
6
7
8
I