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Home ::  Articles ::  Related Articles ::  AGM Carburetor Adjustment Troubleshooting

AGM Carburetor Adjustment Troubleshooting

Carburetor or carb is used to deliver the correct amount of air and fuel mixture at a given throttle opening for an internal combustion engine. It is relatively simple devices. However, as with all mechanical devices, carburetors will wear over time and will also require periodic tuning and service.


Keeping your carburetor and linkages clean and well adjusted is very important for your AGM-30 gasoline engine has a smooth-running. The air coming into the carburetor is clean and free of debris by inspecting the air filter. A clogged air filter is a common cause for black smoke emitting from the exhaust.

The following is a chart of potential gas engine carburetor adjustment problems and possible remedies.

Problem Solution
The engine hesitates when accelerated rapidly
or the rpm increases at idling
or the engine stops when the throttle is moved from high to low.
The low-speed needle "L" is too lean. Open it up about 1/8 of a turn and try again.
If The idle is not steady. The low-speed needle "L" valve is too rich. Close it 1/8 of a turn and try again.
Engine stops at full throttle
or engine hesitates when accelerated rapidly.
or the engine will not come up to full rpm at full throttle.
The high-speed needle valve "H" is too lean. Open it up 1/8 of a turn and try again.
Engine does not reach full rpm
or carbon build-ups appear consistently on your spark plug.
The high-speed needle valve "H" is too rich. Close it up 1/8 turn and try again.

Other problems a carburetor may fall into are: rich mixture and lean mixture. Diagnosing carburetor problems is relatively easy and follows some telltale symptoms.

Rich mixture
The typical symptoms of a rich mixture include: uneven running (will often slow from regular idle rpm's and stop), sooty or black muffler end pipes, sooty or black spark plugs, sluggish acceleration, strong smell of gasoline when machine is at idle, choke not needed from cold starts and poor fuel economy. This means too much gasoline is delivered.

Usually, it is caused by dirty air filters, but it could also result from the owner fitting replacement exhausts and/or carburetor systems. If the fuel level is set too high in the float chamber, a rich mixture will result.

Lean mixture
This is quite the reverse. Lean mixture means too much air is delivering by carburetor. The symptoms include bluing (on chrome systems) of the exhaust header down-pipes, backfires as the throttle is closed (primarily during coast-downs), white or light grey spark plugs, lurching acceleration, requires excessive amounts of choke to run/start and more.

Generally, it is caused by the owner fitting after-market accessories such as exhaust systems, air filter systems or replacement carburetors of a different type or size.

Each incident varies in accordance to individual use. It is recommended to inspect carburetor parts regularly.