Yamaha MM700A, Manual, Page: 133 / 282

FUEL AND EXHAUST SYSTEMS
127
CARBURETOR OPERATION
(THROTTLE OPENING 0 TO
Pilot outlet
Air
Pilot jet
CARBURETOR OPERATION
(THROTTLE OPENING
118
TO
Air
Jet needle
Needle jet
CARBURETOR OPERATION
(THROTTLE OPENING
Air
(Figure 4). As the throttle is opened further, the air stream
begins to siphon fuel through the main jet and needle jet.
The tapered needle increases the effective flow capacity
of the needle jet as it rises with the throttle valve, in that it
occupies decreasingly less of the area of the needle jet
(Figure 5). In addition, the amount of cutaway in the lead-
ing edge of the throttle valve aids in controlling the
mixture during partial throttle openings.
At full throttle, the carburetor venturi is fully open and
the needle is lifted far enough to permit the main jet to
flow at full capacity. See Figure 6 and Figure 7.
CARBURETOR SERVICE
1. Open the shroud.
2. Remove the air box as described in this chapter.
3. On models equipped with a carburetor heating system,
make sure the control knob
(Figure 8)
is
turned
OFF.
NOTE
The heater hose is connected to both
end
carburetors.
4. Position rags or a receptacle under each heater hose fit-
ting
(Figure 9) to catch coolant. Then disconnect the
heater hoses from the carburetor.