Repair And Fix it

Over the years, various models of carburetor chokes have been developed in order to facilitate different engine conventionalities such as differing engine designs, varying load requirements and air/fuel intake varieties. In essence, the varieties of carburetors have been specifically designed to provide an assortment of drafting amounts, a multitude of barrels and varying venturi and flow rates.

Carburetor Draft

The variation in draft technology is one way in which carburetor chokes can be classified. Drafting within carburetors can be defined as sucking in or exhaling out air. There are three main types of drafting technologies that can be incorporated into carburetors. These are downdraft, sidedraft and updraft models. The downdraft and updraft technologies work using a method completely opposite to each other. Downdraft allows air to flow through the engine in a downward direction whereas the updraft variety allows air to be transferred through the engine in an upward direction. On the other hand, the sidedraft variety allows air to flow through the engine in a horizontal manner. Sidedraft technology was incorporated into older vehicle models whereas downdraft technology is used in cars these days. However, updraft carburetors are used in machinery such as forklifts.

Carburetor Barrels

Carburetor barrels can basically be defined as a hollow cylinder in which air and fuel is mixed by the engine. The basic parts are the throttle plate, air horn and venturi. There are three essential types of carburetor barrel models; one-barrel, two-barrel and four-barrel carburetors. The one barrel model is primarily incorporated into small engines that do not require a lot of power such as a motorcycle. On the other hand, a two-barrel system is used in cars with large engines and comprises two throttle plates and double venturis. A four-barrel model is used with trucks and SUVs because it has the ability to provide a large amount of engine force. Under normal conditions, the engine uses only two of the four barrels. If extra power is required, the other two barrels are employed to mix in more fuel and air.

Feedback Carburetor System

In accordance with technological breakthrough of todays day and age, car makers have developed an electronic carburetor system that has the ability to provide highly efficient energy by electronically maintaining the levels of air and fuel. The electronic carburetor is used in almost all of the cars being built today and also has the ability to reduce pollution by oxidizing HC and CO as well as reducing the amount of nitrogen oxide expelled into the air. The entire system uses a three-way catalytic converter which maintains the most efficient mixture of air (oxygen) and fuel.

The function of a carburetor is to regulate the engines fuel air mixture. If the mixture is too rich, meaning the air content is too low, increased carbonization of the engine can occur. It can also decrease engine performance and increase the chances of smoking. If the mixture is too lean, or the air content is too high, there is less lubrication to the engine which could cause cylinder scoring. Maintaining the proper fuel air ratio is necessary to avoid these problems. This can be done by adjusting the fuel air mix. For most carburetor models, special tools are required to adjust the carburetor. These tools adjust carburetor-specific screws which are now used on most models to prevent adjustment by non-EPA-certified mechanics. Five different carburetor adjustment tools are currently on the market.

Single "D"-shaped Tool

The single "D"-shaped carburetor adjustment tool is used to adjust the tamper-proof adjustment screw found on some carburetor models. Both the tool and the tamper-proof adjustment screw are "D"-shaped. The adjustment of the screw changes the amount of air that is allowed into the engine. By turning the screw in, the amount of air allowed into the engine is reduced, creating a rich fuel air mixture. By turning the screw out, the amount of air allowed into the engine is increased, creating a lean fuel air mixture.

Double "D"-shaped Tool

The double "D"-shaped carburetor tool is used to adjust the double "D"-shaped tamper proof adjustment screw on small engine carburetors. This is done while the engine is running and has had a chance to warm up. This is because the carburetor settings will change once the engine has warmed up.

Hex-shaped Tool

The hex-shaped carburetor adjustment tool is used to adjust the tamper-proof adjustment screw on both small and large engines. The tamper-proof adjustment screw is generally blocked with a cap by the manufacturer to prevent adjustment of the carburetor by non-licensed professionals. Special tools are required for the removal of the cap. The distribution of the cap removal tools are also regulated by the EPA.

Pac-man-shaped Tool

The pac-man-shaped tool is used for the tamper-proof adjustment screw on some Walbro and Zama carburetor models. These tools are also referred to as V-notch carburetor adjustment tools. They are offered to certified mechanics through MTD distributors.

Splined Tool

The splined carburetor adjustment tool is generally used to adjust the tamper-proof adjustment screw on Poulan and Weedeater carburetors. These tamper-proof adjustment screws have four sets of splines each spaced 90 degrees apart.