Generator choke

Do you own a generator?

A generator choke is an important part of your generator. It helps the engine start and run properly. Without a working choke, your generator might not work at all.

We want to help you keep your generator running properly. That’s why we’ve put together this guide on the choke on a generator. We have you covered on how to use it to fix it. So keep reading for more information on this essential piece of equipment.

Follow our guide on how to use a choke on a generator now!

What a Choke Does on a Generator?

The carburetor draws the fuel from the fuel line (connected to the fuel tank) into the fuel bowl. Then through the main jet, it is fed to the emulsion tube. In addition, the carburetor takes air from outside to mix them into a combustible mixture that is fed to the combustion chamber. The correct fuel-to-air ratio is paramount for proper combustion.

The choke on any portable generator is a lever that controls the air supply to the carburetor. The throttle works properly in a warm engine, but the liquids don’t get vaporized easily in a cold environment. You need a richer fuel mixture to start a cold engine. This is the basic function of a choke lever.

It closes to allow less air, thereby enriching the mixture to facilitate the cold start. While not very efficient, it is an effective way to ensure that your generator starts in cold conditions. Once your engine warms, you can open the choke lever to allow more air for fuel to burning cleanly and efficiently.

How Does A Generator Choke Work?

Let us briefly familiarize you with the basic functioning and operation of the choke, which will allow you to check and troubleshoot if it is not functioning properly. The discussion is limited to the functioning of an electric choke.

Old Delco Type Chokes

The old generators carry Delco-style chokes. In this system, a bimetallic coil spring is warmed by the heat from the hot air from the engine and the 12 V heater element. The strip is mounted between the housing cover and the choke lever. As a result, it expands and actuates the choke mechanism. The heater element accelerates the opening of the choke to reduce emissions.

The spring tensions were adjusted so that the butterfly remained open on a cold engine. As the temperatures drop, the coil spring will contract to close the choke. In most engines, reducing the clearance between the top edge of the butterfly and the carburetor air horn to the range of 1/4 to 3/8 inches will let the generator start.

Mitsubishi / Homelite type chokes

They introduced flat bimetallic strip type chokes instead of coiled ones. Mitsubishi design used a supplementary vacuum actuator in addition.

Thermistor Controlled Solenoid

Thermistors, as the name suggests, are resistors whose resistance values change with temperature. In a positive temperature coefficient (PTC) thermistor, the resistance increases with temperature, while in a negative temperature coefficient (NTC) thermistor, it decreases.

In many of Honda’s designs, PTC is mounted on the cylinder head and cuts the power supply to the choke solenoid as the engine warms, opening the choke. The thermistors are also sometimes called thermoswitches. Honda has different settings for trigger temperatures in each of its generators.

Auxilliary choke

Some EB series generators from Honda carry a vacuum actuator-operated auxiliary choke that remains in the closed position as the engine starts. The manifold vacuum pulls the butterfly to the open position once the engine reaches its full speed.

Where Is The Choke On A Generator?

The passageway in the carburetor (after the main jet) reduces in size and becomes narrower towards the throttle plate. This passageway is known as the Throat or the Venturi. The choke lies in the throat between the air filter and the throttle plate.

Can You Leave the Choke Closed on a Generator?

The simple answer to this query is “No.” As you operate your generator with more fuel than the optimal mix, part of the fuel remains unburnt and is exhausted as such. You may also experience excessive & black smoke with the characteristic smell of the fuel in the generator’s vicinity. This video explains all this in detail.

In some cases, if you let the generator run with a closed choke, the engine may shut down automatically. Even in a machine running with a partially closed choke position, you will face gas wastage and black exhausts.

Generator Choke Problems

You may experience problems like

  • The generator not starting,
  • The generator started but turned off when the choke was opened. Again, it runs if the choke is fully or partially closed.
  • Leakages in the air system,
  • The choke is not functioning.

Let us discuss these issues one by one, so you can check and troubleshoot the problems.

The generator not starting.

There can be many reasons associated with the generator not starting. We have a detailed and dedicated article on the subject, where we dealt with issues with the battery, spark plugs, oil level, compression system, etc.

With regard to the choke, you need to check if the choke is in an open position, particularly in cold conditions. We have already discussed the implications in detail above.

Generator Stalling on opening the choke.

It is possible that the generator starts with the closed choke but stalls on opening it again. However, the unit runs in a full-choke or half-choke position. As the problem occurs on opening the choke fully, it indicates an improper fuel-to-air ratio, which can be caused by a lower fuel supply, more air flow, or both. Let us see the reasons below:

Use of stale fuel:

As most manufacturers recommend, you should not leave your gas tank for more than 2 to 3 months unless you are using a fuel stabilizer. Untreated stored gasoline will cause harm to your engine and will be less combustible when the choke is opened. You need to drain all the gasoline from your gas tank and fuel bowl. Then clean the entire fuel system before refueling with fresh gasoline.

Fuel restriction in the fuel system:

In the closed position of the choke, a vacuum gets created in the throat area, pulling the fuel from the bowl and through the main jet, pilot jet, and other ports to the cylinder’s intake valve, aided by the downward stroke of the piston.

When the choke opens, the suction action for the fuel reduces, particularly if the jets or other ports are clogged. This usually happens as a result of varnish formation caused by evaporation of the fuel. Opening the choke leads to a high air-to-fuel ratio, and a reduction in fuel supply makes it worse, resulting in what is known as a lean mixture.

Chances of gum formation due to fuel oxidation are more at the bottom of the main jet, the lowest point in the fuel system inside the carburetor. You need to close the main fuel valve and drain the bowl through the drain screw. Then remove the bowl, the main jet, and the emulsion tube, and clean them with the carburetor cleaner. You can use a wire brush or a single twist of a wire to open out the holes. We have detailed the steps in our other article on cleaning the carburetor.

The fuel passes through the pilot jet in idle conditions in many of the engines. It can also lead to similar problems if restricted and needs to be also cleaned if clogged. If you experience rough operation in idle mode, your idle jet is, in fair probability, clogged.

Leakages in the air system

Other reasons for the high air-to-fuel ratio are (a) a loosely mounted carburetor or (b) damage to the gaskets (head and flange) between the carburetor and the generator body. This will lead to more air getting sucked into the engine resulting in an overly lean mixture that increases the combustion temperature.

Choke not functioning

Once you have zeroed down the problem to lie with the choke, after ensuring that the other elements are working correctly, let us review the checks required to determine the issues with it.

How To Test & Fix A Choke On A Generator?

The first and obvious step is verifying the butterfly’s movement on its pivots. If required, you might have to clean the affected surfaces with a carb cleaner. However, do not attempt to disengage it from its fixtures.

If the choke works with a vacuum actuator, check the actuator for any vacuum leak. In addition, inspect the vacuum lines for any visible cracks.

If the choke uses thermoswitches, test them with an ohmmeter. If it shows infinite resistance, the thermo switch needs replacement. On the other hand, zero resistance indicates issues with the wiring. You may apply a small amount of heat to the switch, resulting in an increase in the resistance value.


That’s all for this blog post on chokes. I hope you found it informative and helpful. If you have any questions or need clarification, please let me know in the comments section below, and I will do my best to help you out. Have a great day!

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