Yamaha FT50C Service Manual page 15

Carburetor operation
1. Idle and low-speed operation
Since the vacuum at the venturi is low when the throttle valve is opened slightly, the main nozzle
does not supply any air-fuel mixture to the engine.
When the engine is operating at idle, the fuel that passes through the pilot jet and the air that passes
through the pilot air jet mix, enabling the air-fuel mixture that has been regulated by the pilot screw
to be fed through the pilot outlet.
Because the throttle valve opens slightly when the engine is operating at low speeds, air-fuel mix-
ture also starts to be fed from the bypass holes.
1 Pilot screw
2 Pilot outlet
3 Bypass holes
4 Venturi
5 Main nozzle
6 Pilot jet
7 Main jet
8 Pilot air jet
62Y5A11
3 3
2 2
2 2
1 1
0 0
9 9
8 8
5 5
6 6
7 7
9 Main air jet
0 Throttle valve
È Air
É Air-fuel mixture
Ê Fuel
Technical tips
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4 4
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