Carburetor Systems

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

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

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

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

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

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

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

Choke Coil Operation

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!

Altitude Compensator Compensates for altitude Adjusts an air bleed

Idle Speed Control

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