Yamaha F4B Service Manual page 40

TECH
FEA
High speed operation
When running at high speed, the throttle valve opening is near the fully open position, and the neg-
ative pressure generated in the main bore a becomes even higher. Consequently, a larger amount
of air and fuel mixture is drawn from the main nozzle a to be supplied to the engine.
At high speed operation, as the negative pressure in the main bore a becomes higher than the neg-
ative pressure in the pilot passage b, fuel is not drawn through the pilot jet c.
A Air
B Fuel
C Air and fuel mixture
2-11
Technical features and description
c
b
a
a
A
B
C