1. Carburetor Systems

2. Fuel inlet system Stores fuel for immediate use Maintains level Viton Needle, brass seat Dampening spring Vapors vented to carbon canister The Float Bowl

3. Idle Circuit • Low airflow @ idle, main system will not operate • High vacuum under throttle plate draws fuel out idle ports • Sometimes adjustable • Idle air bleed helps atomize fuel

4. Transfer Circuit • Adds fuel as throttle plate opens, overcomes “lag”

5. Main Metering Circuit • Fuel supplied by “main jets” • High venturi vacuum creates low pressure at nozzle tip • Atmospheric pressure in float bowl pushes fuel out discharge nozzle

6. Power Circuit • Provides extra fuel at WOT • Mechanical power valve, maybe adjustable • Sometimes combination with metering rods • Flows through a circuit into main metering system

7. Accelerator Pump • During sudden acceleration, mixture leans out • Pumps a lot of fuel into venturi

8. Choke Circuit • Very rich A/F needed on cold starts • Closes off top of venturi to raise the vacuum level allowing greater fuel flow into manifold • Opens as engine warms up, or as an electric coil heats up

9. Choke Coil Operation

10. Choke Pulloff • Forces the choke open slightly just after engine starts. • Position determined by • torque of coil • air velocity on blade • vacuum on piston • must adjust correctly!

11. Altitude Compensator • Compensates for altitude • Adjusts an air bleed

12. Idle Speed Control

13. Throttle Kicker • Electric motor or solenoid, increases idle 1. Dashpot, 2. Throttle kicker, 3. Throttle cable, 4. Idle adjustment