Carburetor - Yamaha F4B Service Manual

TECH
FEA

Carburetor

Idle and low speed operation
When the engine is running at idle or at low speed, negative pressure generated in the pilot passage
a will be increased.
Air is drawn into the pilot passage through the pilot air jet b to be mixed with the fuel that is also
sucked into the passage through the pilot jet a. This air and fuel mixture is supplied to the engine
through the pilot hole c. The pilot screw b controls the amount of air and fuel mixture that will be
supplied to the engine.
When running at low speed, the air and fuel mixture is supplied to the engine through the pilot hole
c and through the bypass holes d.
A
c
A Idle operation
B Low speed operation
C Air
D Fuel
E Air and fuel mixture
2-9
Technical features and description
b
a
B
b
c
a
d
b
a
b
C
D
E