1. Define Carburation
In an internal combustion engine, the process of producing a mixture of air and fuel in the correct proportion for engine combustion is called carburation.

2. Air-Fuel Ratio
Fuel alone cannot burn. It must be combined with the oxygen in air to form a combustible mixture. The perfect balanced air to fuel ratio by mass is 14.7 to 1. This is 14.7 parts of air to one part of fuel. At this ratio under ideal conditions all of the fuel and oxygen will be consumed by combustion. This is called a stoichemetric ratio

4. Air-Fuel mixture requirements

5. Air Fuel Ratio and Pollution

6. What is a carburetor?
Carburetor is the part of a gasoline engine which provides the mixture of gasoline and air that the engine burns.
The carburetor mixes gasoline with about 15 times its weight in air for the engine to run smoothly at all speeds.
A driver controls the engine speed by increasing or reduction the flow of the fuel mixture.

8. Types of Carburetors There are three common types of carburetors
Natural or side draft
Updraft
Downdraft
Another type of classification
Fixed choke
Constant depression

9. Side Draft

10. Down Draft

11. Updraft

12. The Simple Carburettor Petrol Operation of the Venturi
The Float Chamber
Petrol
Operation of the Venturi
Choke Valve closed
The Throttle Valve controls the amount of air fuel mixture entering the engine and therefore engine power
The Choke Valve is used to provide a rich air/fuel ratio for cold starting