What causes a small engine to rev up and down? A lawnmower that hunts and surges may be experiencing something as simple as an airflow issue. If the air that the engine requires to run is blocked, especially sporadically, it can cause the engine to slow down. When the blockage moves or clears, the engine may suddenly rev up in response.

Why is my small engine surging? Problems in the Fuel System

Check and clean the vent. Surging is also caused by water that got into the fuel. A mower left in a heavy rain or condensation on a hot summer day can choke the engine. Empty the gas tank, properly dispose of the old fuel and try a fresh batch of gasoline.

What causes lawn mower engine surging? The most common reason for a surging lawn mower engine is a blockage in the fuel supply, but there are other possibilities: Bad gas. Bad spark plug. Dirty / faulty carburetor.

Can spark plugs cause surging? 3. Surging and Lagging. Another good indication that your spark plugs are dirty or worn is if your vehicle experiences surges of speed, resulting in a jerking acceleration. These surges occur because your spark plugs are not igniting the fuel in your engine at the proper rate, resulting in an uneven speed.

What causes a small engine to rev up and down? – Related Questions

What causes an engine to hunt and surge?

If an engine is not getting enough fuel (this is called “running lean”), due to fuel pressure (regulated by the fuel pump and regulator), restricted fuel injectors, a vacuum leak or really anything that throws off the fuel mixture going in to the engine, this can cause the surge.

How do you adjust a carburetor on a lawn mower?

Set the throttle to fast and start the mower engine. Turn the high speed screw first clockwise until the engine slows, then counterclockwise until it slows. Locate the center point where the engine idles best. Move the throttle from slow to fast then back to slow to test the adjustment.

How do you adjust the governor on a Briggs and Stratton 19.5 hp?

To adjust the governor, you would loosen the screw on the bottom of the governor arm and push the governor arm so the throttle is wide open. Then you would turn the bottom “clip” (which is connected to the governor shaft) counter clockwise. This will set the governor shaft on top of the governor spool.

How do you adjust the carburetor on a Briggs and Stratton engine?

Locate the idle adjustment screw on the side of the carburetor. It sometimes has a spring wound around the shaft. Turn this screw clockwise with a Phillips screwdriver until you encounter resistance, which means it has contacted the carburetor seat. Back it off 1 to 1 1/2 turns.

How does the governor work on a small engine?

To control engine speed, a mechanical governor uses gears and flyweights inside the crankcase to detect changes in the load and adjusts the throttle accordingly. This closes the throttle, limiting the air-fuel released into the engine. When the engine load increases, the crankshaft spins more slowly.

How do you adjust the governor on a Briggs and Stratton 6.5 HP?

First, loosen the arm until it is moving freely. Next, open the throttle to full capacity while making a note of which direction the arm moves in when the throttle moves through it. Once the throttle is fully opened, move the governor shaft in the same direction the governor arm traveled.

Why is my Kawasaki engine surging?

Surging is usually lack of fuel. Surging at low idle is usually a blocked idle circuit in the carb. Before you do that check for leaks by spraying around the carb and in particular the manifold with WD 40 or similar FROM A TRIGGER PACK. Any change in the engine running will indicate a fuel leak.

How do you adjust the governor on a Kawasaki engine?

To adjust the governor, you would loosen the screw on the bottom of the governor arm and push the governor arm so the throttle is wide open. Then you would turn the bottom “clip” (which is connected to the governor shaft) counter clockwise.

What is a welch plug in a carburetor?

Welch plugs are small, cupped disks that are usually made of aluminum or steel. Welch plugs seal air and fuel passages running through a lawn mower carburetor. A carburetor controls an engine’s airflow to regulate the amount of air pressure entering the engine.

Can bad spark plugs cause idle surge?

Weak Ignition from Damaged Spark Plugs

Failing spark plugs can cause more than just surges or misfires. For instance, your car might sound rough when it’s idle. Not only that, but it can also cause you some problems when trying to start the engine. Moreover, modern cars can cause position sensors to fail, as well.

What does car surging mean?

Surging is associated with a sudden increase in speed that occurs while trying to maintain a constant one. This is a sign that your fuel pump may have sufficient wear and tear and that its irregular resistance within the motor is creating an inability to maintain consistent pressure resulting in surges of power.

What position should the speed control be in when adjusting the governor?

Rotate governor lever clockwise so that throttle is in full wide open position. Throttle stop must contact cast stop on the carburetor.

How do you fix an idle surge?

Turn the engine off again, and reattach the air intake duct work to the throttle body. Start the engine and rev and hold to 1,500 to 2,000 rpm until no white smoke is coming out of the exhaust pipe. Cleaning the Idle Air Speed Control Valve with aerosol throttle cleaner can often solve an idle problem.

What causes RPM to fluctuate while idling?

Why does my engine’s RPM seem to fluctuate (runs rough)?

Many engine performance problems can be linked to maintenance issues such as stale fuel, dirty air filter, fouled spark plug, and deteriorated oil. Engine hunting and surging at idle is usually caused by a fuel delivery, air leak, or governor system problem.

What does it mean if your RPM go up and down?

It sounds like you have a dirty or failing air control valve. The job of the idling air control valve is to bring this deceleration down to a slow and smooth idling rather than cutting off the fuel supply and causing the motor to die.

How do I know if my carburetor is rich or lean?

Q: How Do You Tell if a Carburetor Is Rich or Lean? A: One way to tell for sure is by “reading” the spark plugs. If the plug tip is white, the mixture is lean. If it’s brown or black, it’s rich.

Why is my Kohler engine surging?

surging on a governed engine is always due to an fuel;air ratio that is too low. The fuel supply to the main jet is not enough. You test for the first by starting the engine and saturating the area between the carb & the engine with WD 40 or similar from a trigger pack, not a spray can.

How do you adjust the governor on a Briggs and Stratton 10 hp generator?

To reset the governor.. hold the throttle all the way open. Turn the governor shaft counterclockwise until it stops. Now tighten the nut up.