The metering rod on a Carter WO carburetor plays a critical role in regulating the air-fuel mixture, especially during changes in engine load and throttle position. Here’s how it works:
Function of the Metering Rod in a Carter WO Carburetor
Location and Basic Setup:
The metering rod is positioned vertically inside the carburetor and is connected to the accelerator linkage at the top.
The rod moves up and down within the main jet, which is the orifice through which fuel flows from the float bowl to the venturi.
Tapered Design:
The metering rod is tapered, meaning it is thinner at the tip and gets thicker toward the top.
When the thicker part of the rod is inside the jet, less fuel can flow.
When the thinner portion is inside the jet, more fuel can flow.
Idle and Light Throttle Operation:
At idle or low throttle, the metering rod is at it's lowest position.
This reduces fuel flow, providing a leaner mixture suitable for idle or cruising conditions.
Acceleration and High Load:
As you open the throttle the metering rod is pulled up out of the main jet allowing more fuel to flow through.
Now the thinner part of the rod is in the jet, allowing more fuel to flow, enriching the mixture for power and acceleration.
Summary
The metering rod in a Carter WO carburetor acts like a variable fuel restrictor. It automatically adjusts fuel flow based on engine demand—leaning out the mixture at idle and cruising, and enriching it under load—helping to balance performance, economy, and drivability.
