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How to Adjust a Briggs Carb Needle Valve

2012-07-17

Briggs and Stratton engines use two primary types of carburetors: diaphragm and float. Diaphragm types use a diaphragm pump to control fuel delivery while a float type uses gravity and a float controlled needle valve to control fuel flow. Both types also have an air-fuel mixture valve, which is used to control the ratio of air to fuel entering the engine. This air/fuel needle VALVES can be adjusted from a very lean mixture to a very rich mixture

Instructions

- 1
  
  Screw in the air/fuel mixture needle valve until it stops. Do not screw it tight. That could damage the needle.
- 2
  
  Unscrew the valve about 1 1/4 turns. Start the engine.
- 3
  
  Unscrew the needle valve more until the engine speed starts to drop due to the air/fuel mixture being too rich.
- 4
  
  Tighten the screw about one half of a turn or until the engine speed is at its peak during the adjustment. Most lawn equipment will lean slightly on the rich side of the air/fuel mixture scale.

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How to Adjust a Briggs Carb Needle Valve

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