Carburetor Metering Diaphragm 'HOW IT WORKS' 2Stroke Carburetor

Uniquely explained like never before, this video will give you a firm understanding of how this system works on a two stroke carburetor. Having this knowledge give you for more confidence when undertaking any adjustments and repair work on these small but tricky carburetors. I really hope you enjoy. Craig

A metering diaphragm is a crucial component in a 2stroke carburetor that helps control the flow of air and fuel into the engine's combustion chamber. Its primary function is to regulate the mixture of air and fuel to maintain the proper airtofuel ratio for efficient engine operation. Here's how a metering diaphragm works in a 2stroke carburetor:

Location: The metering diaphragm is typically located within the carburetor body, sandwiched between the carburetor's main body and the carburetor cover or top plate.

Air and Fuel Flow: In a 2stroke engine, air and fuel need to be mixed in specific proportions to ensure proper combustion. The metering diaphragm is responsible for controlling the flow of fuel from the carburetor's fuel reservoir into the carburetor throat, where it mixes with incoming air.

Vacuum Operation: The metering diaphragm operates in response to changes in engine vacuum, which are created as the engine's piston moves up and down in the cylinder. When the piston moves downward (during the intake phase), it creates a vacuum within the carburetor, which acts on the metering diaphragm.

Diaphragm Movement: The metering diaphragm consists of a flexible, rubberlike diaphragm material and a rigid backing plate. When engine vacuum increases, it exerts a suction force on the diaphragm, causing it to move downward. This movement creates space in the carburetor throat, allowing more fuel to flow from the fuel reservoir into the airstream.

Spring and Needle Valve: To regulate the fuel flow, the metering diaphragm is connected to a springloaded needle valve. As the diaphragm moves in response to changing vacuum, it adjusts the position of the needle valve. When the diaphragm is pulled down by high vacuum, it opens the needle valve further, allowing more fuel to flow. Conversely, when vacuum decreases, the diaphragm moves upward, reducing the opening of the needle valve and limiting fuel flow.

Maintaining the Mixture: The metering diaphragm's action ensures that the airtofuel mixture remains consistent across different engine operating conditions, such as idle, partthrottle, and wideopen throttle. This is important for the engine to run efficiently and smoothly at all RPM ranges.

Tuning: Carburetors often have adjustment screws or settings to finetune the airfuel mixture, which can affect the metering diaphragm's operation. By adjusting these screws, you can control the diaphragm's response to engine vacuum and, consequently, the airfuel ratio.

In summary, the metering diaphragm in a 2stroke carburetor plays a crucial role in regulating the flow of fuel into the engine based on changes in engine vacuum. It ensures that the engine receives the correct airfuel mixture for optimal performance and combustion efficiency across different operating conditions. Proper tuning and maintenance of the carburetor, including the metering diaphragm, are essential for the engine's performance and reliability.

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This principle works for most types of Chainsaw saws, and the following also helps with Chainsaw maintenance. So, whether you are using a Stihl Chainsaw, Husquvarna Chainsaw, basically, all types of Petrol Chainsaw are valid for this principle, as well as many types of or a 2 Stroke Engine. The Electric Chainsaw, of course, escapes this whole principle!

I wanted to upload this shortened version so as to make it a easier for viewers find this specific type of material should they need to.

I really hope it is useful to you.

Thank you

Craig Kirkman (Owner and Creator of the 'The Repair Specialist' Channel).

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