Generator Care Generator Maintenance

How Adjust Generator Carburetor (Troubleshooting and Speed Change)

A generator carburetor is a crucially important piece in engine combustion and speed. To achieve smooth running, your generator’s carburetor and the linkages must stay clean and adjusted properly. If the generator engine runs rough, adjusting the mixture and setting the right idling speed can decrease its stress and prevent it from running too fast or too slow. So, how do you make the necessary generator carburetor adjustment?

You want to start by ensuring the carburetor and the air filter are clean to prevent the generator from surging up and down, making it difficult to set the RPM. While cleaning the carburetor, check the status of the fuel jet to make sure it’s not gummed up or blocked by debris. When done, you can make the necessary carburetor-governor linkage configurations.

Generator carburetor adjustment might sound simple, but if you go wrong, the engine might run too fast, causing catastrophic failure or too slow, reducing its power production efficiency. If you’re not confident enough to do this, it’ll be best to leave it to a professional.

What to Do Before Making Any Generator Carburetor Adjustments

Ensure the air coming from the air filter getting into the carburetor is clean with no debris. Inspect the air filter for any clogging, the main cause of black smoke from the exhaust.

Check if the linkage attaching to the choke plates and carburetor throttle does not bind or stuck, something common when they get dirty.

If your generator carburetor has mixture screws (check the user manual), they could be affected by constant generator vibration or wear.

When the generator runs outdoors, the carburetor’s passages might also be affected by deposits that find their way into the carburetor.

They can clog the fuel and air passages, thus reducing the generator performance or even stopping the engine altogether.

The good news is, with enough confidence, you can solve all these problems easily and quickly. You might not even need to remove the carburetor from the generator. You can also use a carburetor clean to give the piece periodic cleaning inside out.

With most generator performance decrease linked to maintenance issues such as dirty air, stale fuel deteriorated oil, or fouled spark plug; you can avoid them by using a generator engine maintenance kit to perform yearly tune-up.

Generator Carburetor Adjustment: Fuel Supply Problem Troubleshooting

Clean the carburetor

Depending on your generator, locate the air filter and remove it. Once it’s out, you should be able to see the choke at the carburetor throat opening mounted on a shaft. Inspect to make sure it moves freely. If it doesn’t, it could lead to engine starting issues.

An easier way of troubleshooting this is to degrease the carburetor by applying some carburetor cleaner on the sluggish choke shaft and inside the venturi to try and loosen the grit.

Even though it’s a rare thing, don’t forget to remove any debris you come across when cleaning the carburetor.

Inspect the Fuel Valve

Locate the fuel valve, mostly found under the fuel tank. Remove the line and check for a clog or blockage.

When closed, fuel will not reach the carburetor, which will affect the generator speed and performance.

Check the Spark Plug

Remove the spark plug and inspect it for wetness or dryness. If its tip is wet, it could mean over-choking, excessively rich fuel mixture, or water in the fuel.

If too dry, it could mean a clogged air filter, clogged or stuck carburetor inlet needle, or leaking carburetor mounting gaskets.

The best and easy way to solve this is to pour a teaspoon of fuel into the combustion chamber through the spark plug hole. You can screw the spark plug and start the generator.

If your engine starts, it’s probably a dry plug causing the issue, something that will need you to make some generator carburetor adjustment or disassembly and repairs.

Generator Carburetor Adjustment: Idle Speed and Air-Fuel Mixture Adjusting

One of the carburetor adjustments you can do to tune up your generator to increase its engine RPM when it reduces its efficiency is to adjust the air-fuel mixture and the idle.

You should locate the idle speed screw or a tab holding to a spring that controls the governor arm responsible for preventing the throttle from closing completely. Some generators also come with an idle screw that controls the fuel flow when the engine idles.

With your generator engine off, you can remove the air filter, including the cover and cartridge. Using the user manual, locate the idle mixture adjustment screw and rotate it clockwise. Wait until the idle needle touches the seat before turning it counterclockwise one and a half turns.

Check for a main jet adjustment screw in your generator’s carburetor at the float bowl base. If yours has it, turn it clockwise till you feel it touching the seat before turning it counterclockwise one or one and a half turns.

Now you can replace the air filter assembly and start the generator to make the final idle speed and air-fuel mix adjustments.

Allow the generator engine to run for 5-minutes at half throttle to give it time to reach the normal operating temperature.

When the wait is over, turn the idle mix screw to the clockwise direction until the generator starts to slow down. Turn the screw anticlockwise direction until the generator speed starts to slow down again. Finally, adjust the screw until you reach the midpoint.

Use a tachometer to check the engine speed. Adjust the idle screw and bring the engine speed to 1200 RPM for a generator with cast-iron cylinder sleeve engine or 1750 RPM for a generator using an aluminum-cylinder engine.

Hold the throttle lever and the idle speed adjusting screw while the generator is running idle to get its speed true idle. You can repeat the idle mixture adjustments to fine-tune the adjustments.

Generator Carburetor Adjustment: High-Speed Mixture Adjusting

Some generator carburetors have a high-speed mixture adjusting screw placed near the throttle plate or opposite the idle speed adjusting screw.

When the generator is running on load, a high-speed circuit increases the airflow through the carburetor throat.

High-speed mixture adjusting requires the engine to run at a warm temperature, stop it, make the adjustments, and restart it for a final tune-up.

Start the generator and allow the engine to run for 5-minutes at half throttle to warm it up to the operating temperature and then stop it.

With the engine warm, use the generator manual to locate its high-speed mixture adjusting screw and turn it gently clockwise till the needle touches the seat. Reverse the direction for one or one and a half turns.

Start the generator and set the throttle position to FAST or HIGH. Also, turn the main jet adjustment screw clockwise until the engine speed starts to slow. Reverse the turn until the generator engine starts to slow again. You can now set it to the midpoint.

Once you’ve adjusted it, you can check the generator engine acceleration by moving the speed throttle from idle to fast. Your generator should run and accelerate smoothing. If it’s not, readjust the mixture screws.

Generator Carburetor Adjustment: Choke Linkage Adjusting

Remove the air filter and locate the chock level. Move the controls to HIGH or FAST if yours has them. Locate the governor speed control level.

Behind it is a small tension spring that pulls it away, thus controlling the lever. Adjust the screw using a Phillips screwdriver or tab using a pair of pliers to increase the tension of the spring.

It’d be easier if you did this while the generator is running to measure the engine speed in real-time, but it’s highly risky. Any problem you make will impact the generator’s performance instantly.

Related Questions

How do you tell if a carburetor is rich or lean?

If your generator is hard to start, lacking power, has poor throttle, spattering at high speed, engine flooding or producing exhaust smoke, and reduces fuel efficiency, its carburetor is rich. But if it has high or hanging idle, bogs at high speeds, engine overheats, it’s hard to start during cold start, and experiences carburetor backfires, its carburetor is lean.

About the author

Sharif Gen

Leave a Comment