Mower throttle springs are essential components located near the carb, responsible for regulating the engine's speed and ensuring smooth and efficient operation during lawn mowing.

Throttle Spring Linkage Diagram

A throttle spring is a small mechanical component designed to control the throttle mechanism, which regulates the amount of air and fuel mixture entering the engine to control its speed or power output.

How does a throttle spring work?

In Briggs and Stratton engines, the throttle spring is designed to work in conjunction with the throttle mechanism to control the engine speed.

The throttle spring is typically connected to the throttle linkage or throttle plate and exerts tension on it.

When the engine is started or running, the throttle spring provides a pulling force on the throttle linkage or plate, helping to keep it in a closed or partially closed position.

This restricts the flow of air and fuel into the engine, resulting in a lower idle or reduced speed.

The throttle spring in Briggs and Stratton engines plays a crucial role in maintaining stable and controlled engine operation, providing the necessary tension to regulate the throttle position and ensure proper air-fuel mixture delivery for optimal performance.

Inspecting the throttle springs is an important part of carburetor maintenance.

How is a throttle spring linked?

A throttle spring in Briggs and Stratton engines is connected to the throttle linkage, typically through a hook or loop connection, pin connection, or bracket connection.

This linkage allows the spring to exert tension and control the throttle position.

The precise method of linkage can vary depending on the specific engine model and design, but the objective is to establish a secure connection between the throttle spring and the throttle linkage, allowing the spring to exert the necessary tension to regulate the throttle position.

Shown below are two linkage diagrams for Briggs and Stratton throttle springs. The diagrams depict the most common throttle spring linkage locations for Briggs and Stratton powered lawn mowers.

Briggs and Stratton Throttle Spring Linkage Diagram #1

This diagram shows throttle spring link locations on a Briggs and Stratton engine that uses a typical plastic carburetor with primer bulb.

Throttle Spring Linkage Diagram for Briggs and Stratton Lawn Mower Engine

These engines have two springs, both of which connect to the governor arm on one side.

Spring #1, the shorter of the two, is called an air vane spring (part #790849 on Amazon). It connects from the governor arm to a small metal tab located right next to the governor arm.

Spring #2, the longer of the two, is called a governor spring (part #699056 on Amazon).

It links from the governor arm to the throttle control lever, which is typically located at the front of lawn mowers that are powered by Briggs and Stratton small engines.

Briggs and Stratton Throttle Spring Linkage Diagram #2

This diagram shows throttle spring link locations on older pulse-jet style Briggs and Stratton engines.

Pulse-Jet Style Briggs and Stratton Throttle Spring Linkage Diagram

Pulse-jet carburetors were common on 5-8HP engine models used by garden tillers, too. You may need to tilt your mower to see some of the carburetor linkage, on some models.

Required tools

A few basic small engine tools are required to remove or replace the throttle springs on a lawn mower powered by a Briggs and Stratton engine. These are:

  • Safety gloves and eye protection
  • A small flat head screwdriver - to remove the air filter housing located above the carburetor
  • Needle-nose pliers - to grasp the end of the springs firmly without crushing them

My Carb Looks Different - Any Tips?

Yes. Over the years, Briggs and Stratton has made small changes to their carburetors. While they may look slightly different, they all serve the same purpose of mixing air and fuel and controlling engine speed.

Newer lawn mowers are also using redesigned components to meet CARB compliance goals.

Inside the carburetor is a butterfly valve which connects to a throttle control system on the outside. This throttle control is what the governor arm and/or throttle lever connects to, depending on carb model.

These connections, typically called "linkage", use springs to make the action smoother and to prevent backfires. Even if the carb looks different, the linkage will connect the same components.

Tip: Find those components and you'll have a good idea of the size and length of spring you need to link them, even without a diagram.


  • Throttle springs regulate engine speed near the carburetor in lawnmower engines.
  • They work with the throttle mechanism to control air-fuel mixture and engine speed.
  • In Briggs and Stratton engines, throttle springs apply tension to maintain closed or partially closed throttle positions, reducing speed.
  • Throttle spring linkage methods vary, but they aim to securely connect springs to throttle linkages for position regulation.
  • The article offers diagrams for two Briggs and Stratton throttle spring linkage types.
  • Tools like gloves, screwdriver, and pliers are needed for throttle spring maintenance.
  • Despite carburetor visual differences, Briggs and Stratton models have consistent functions; linkage with springs ensures smooth action and prevents backfires.