You start your generator only to find it’s running roughly once you have all of your items plugged into it. Determining the issue is a must to protect the engine from overheating and damage.

Generac generators bog down and run rough under load when too much load is applied for the size of the generator, the carburetor is dirty, the fuel filter is clogged, the air filter is plugged, the choke is stuck, or the spark arrestor is plugged.

Wait for the engine to cool and remove the spark plug wires before performing any repairs. Follow this in addition to the safety precautions outlined in the operator’s manual to minimize serious injuries.

Generac generator carburetor and air filter housing

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Follow all safety instructions provided in your equipment operator’s manual prior to diagnosing, repairing, or operating.Consult a professional if you don’t have the skills, or knowledge or are not in the condition to perform the repair safely.

6 Reasons a Generac Generator Bogs Down Under Load

Too Much Load is Applied for the Generac Generator Size

Before checking the generator for items that can cause it to run rough, check the load limit of your generator along with the wattage requirements of the items you are running with the generator.

The wattage requirements of the items you are running at the same time must be less than the generator’s load limit. Overloading the generator can cause it to bog down. It can also cause damage to the generator and items connected to it.

Follow these tips to determine the wattage capacity:

  • You will find the wattage of most electrical items listed on a tag attached to the item.
  • Some motors require additional wattage to start an item. In this case, the starting wattage should be used when calculating wattage requirements.
  • Add the wattage of all items that will be plugged into the generator at one time to get a total.
  • This total wattage must be less than the generator’s wattage capacity.

Do not run more electrical items using the generator than it can handle.

Dirty Carburetor on a Generac Generator

Over time, varnish can build up in the carburetor causing it to not function correctly. Varnish is a coating left behind by old gas that will coat the internal parts of the carburetor causing them to become plugged or stop moving.

When this happens, a sufficient amount of gas isn’t able to get to the carburetor and your generator will run rough. In order to fix this, you must remove the carburetor and clean or replace it.

To clean the carburetor, it’s a good idea to take photos through the disassembling process to make sure the small parts are placed in the correct positions when reinstalling the carburetor.

Remove the carburetor from the generator. Remove as much buildup as you can using a carburetor cleaner. If you find any damaged parts, use a carburetor rebuild kit to replace them. Once cleaned and repaired, install the carburetor.

If working with small parts is not something you want to tackle, you can purchase and replace a complete carburetor instead of tearing it apart to clean and rebuild it.

Clogged Fuel Filter on a Generac Generator

A fuel filter is installed on a Generac generator to keep dirt from finding its way through the fuel system to the engine causing wear and damage. The filter can become plugged over time from old or dirty fuel when it isn’t replaced regularly.

When this happens, sufficient fuel isn’t able to get to the carburetor which will cause the generator to bog down or quit running.

It’s best to replace the fuel filter each year when you are running your generator like most homeowners. If you use it more regularly, you must replace the filter more often.

Plugged Air Filter on a Generac Generator

The air filter keeps dirt from entering the air intake to protect the engine from the damage that can occur from just a small amount of dirt or debris.

Just like the fuel filter, you should replace the air filter at least once a year and more often if you use the generator frequently or are operating it in dusty conditions.

In addition to replacing the air filter, you must also keep it clean. This includes checking the filter several times in between replacing the filter to ensure that the filter is kept in good condition and free of dirt and debris.

If you are not cleaning and replacing the filter regularly, the filter can become plugged with so much dirt that the engine won’t get sufficient air. It can cause the engine to bog down, overheat and cause extensive permanent damage.

Check the air filter before each use and clean or replace it if needed. Follow the cleaning instructions found in the Generac operator’s manual. I have included cleaning instructions for a couple of types of air filters below. Consult your manual if you are unsure of how to clean your type of air filter.

Clean a Generac generator foam-style air filter

  • Remove the air filter from the housing.
  • Wipe out any dirt remaining in the air filter housing and cover. Don’t allow dirt to fall into the air intake.
  • Inspect the foam filter for damage and replace it if needed.
  • If the filter is in good condition, clean it in soapy water and rinse it until the water runs clear.
  • Squeeze the filter and allow it to dry.
  • Install the air filter.
  • Reattach the air filter cover.

Clean a Generac generator paper air filter:

  • Remove the air filter from the housing.
  • Wipe out any dirt remaining in the air filter housing and cover. Don’t allow dirt to fall into the air intake.
  • Inspect the paper air filter. Tap the filter to loosen dirt so it falls from the filter. If the filter is very dirty, damaged, or no longer seals the air intake sufficiently, replace it with a new one.
  • Install the air filter.
  • Reattach the air filter cover.

Stuck Choke on a Generac Generator

Another lack of airflow problem that can cause the generator to bog down is when the choke isn’t adjusted after the engine warms to allow sufficient air to get to the engine.

This can be due to forgetting to adjust the choke to the off position once the engine warms. It may also be caused by a bad switch or dial (depending on your model) used to start the generator or a stuck choke.

Clogged Spark Arrestor on a Generac Generator

The spark arrestor screen is a part installed on a Generac generator to prevent sparks and hot material from emitting from the muffler. This is to reduce burn injuries and potential fires.

When this metal screen becomes plugged with a buildup of soot, the generator will begin to run rough and possibly shut down.

Before removing and cleaning the spark arrestor, wait for the muffler to cool to reduce injury. Remove the spark arrestor screen and inspect its condition. Replace the screen with a new one if you find any tears or holes in the mesh screen.

If the screen appears to be in good condition, clean it with a commercial solvent or brush it lightly using a small metal brush to remove soot deposits. Once the screen is clean, place it back onto the muffler.

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