Presentation on theme: "SMALL ENGINES CARBURETION"— Presentation transcript:
1 SMALL ENGINES CARBURETION Principles1. Air Pressure2. Air FlowAir Pressure: Fuel is forced in the intake by a low pressure (vacuum) created by the downward movement of the piston.
2 Air Flow: As air speed increases (throttle opens) air flow through the carburetor also increases. This causes the venturi effect in the carburetor. Atmospheric pressure forces the fuel in the fuel bowl up the main discharge nozzle,and into the air horn.
3 Venturi effect: As air flows across an object the bottom of that object a high pressure is formed. On the top a low pressure is formed by small eddy currents.
5 System Circuits Cold Start Enrichment: Choke, Primer Bulb Float Idle Low SpeedHigh Speed
6 Idle/Low Speed Circuit Work on Manifold vacuumThrottle plate is closed or open partially not enough air flow to create the venturi effect.Gas enters from the Idle low speed gas jet.Air enters from the Idle Air Bleed.Air and fuel mix and pass through an Idle Mixture Screw*, The gas and air then exit the Idle port and or the Low Speed Ports.
15 High Speed Circuit Throttle open at least ¼ throttle. Enough air flows to create the Venturi Effect.Fuel Passes the Main gas jet into the main discharge nozzle.Air enters the Main Air BleedFuel and Air mix in the Emulsion tube.Fuel and air exit the Main discharge nozzle.
17 Float CircuitUsed to maintain the proper fuel level, so the carburetor does not present a lean or rich mixture.Components:(FLO-JET) Float, Bowl, Needle Valve, Seat, Bowl VentComponents:(PULSA-JET) Pick-up Tube, Fuel Pump, Gas Well (with spill way)
19 Choke CircuitUsed to Enriched the Fuel and Air mixture under cold start conditions.Components: Choke shaft, Choke PlateOperation: Creates Manifold vacuum Behind the choke plate so that all orifices have fuel exiting from them