Carburetor Inner Passages - TOHATSU MX 50D2 Service Manual

Fuel System

3. Carburetor Inner Passages

1) Idling Passage
a
å
#2, #3 carburetor only)
a - Air intake
b - Air-bleed inlet
c - Slow air jet
d - Bypass port
e - Pilot screw
f - Idle Port
g - Throttle valve
As engine rotates, piston moves from top dead center toward bottom dead center, the piston movement causes vacuous
area to occur in the back of throttle valve.
Then, the air enters carburetor through air intake port, runs through throat venturi and throttle valve, and then is sucked into
the vacuous area in the cylinder that is in air intake stroke.
The float chamber receives atmospheric pressure through air vent. This pressure causes fuel to be sucked into vacuous
area in the back of throttle valve. The fuel is sent to main fuel well through main jet, runs through idle passage, slow jet,
bypass (off idle) port, and then is ejected from idle port. When this fuel goes through bypass port, it is mixed with air in the
carburetor bore to be air-fuel mixture which is sucked into the cylinder.
4-10
b
k
c
j
d
i
h - Fuel inlet
i - Main jet
j - Slow jet
k - Choke valve
å Air
∫ Air-fuel mixture
GB
e
f
g
∫
h
2st 50D2 2011