How to Adjust the Throttle on a Briggs and Stratton Lawnmower, step by step


Does your garden mowing sessions take almost an eternity for you to finish? At some point, you start thinking about how to boost your Briggs and Stratton lawnmower’s cutting speed and save yourself some precious hours. The solution to this problem lies in adjusting your throttle settings. Fortunately for you, this is possible. In this blog post, we shall explain the entire procedure step-by-step.

How to adjust the throttle on a Briggs and Stratton lawnmower, step-by-step:

  • Step 1: Initial preparations
  • Step 2: Remove the outer components to access the governor of your engine
  • Step 3: Measure the clearance between the choke arm and control lever. Adjust it to a prescribed value by loosening or tightening the throttle cable.
  • Step 4: Adjust the governor arm by rotating its pin.
  • Step 5: Reassemble everything and test the mower for performance

Your Briggs and Stratton lawnmower engine has a choke lever situated outside just near the handle. The lever, when set to ‘fast,’ provides maximum engine speed. When the lever is pulled, you adjust the governor arm position to send maximum fuel mixture to the engine for a higher combustion rate and a higher speed. Sometimes, the cable gets loose, due to which you might notice a drop in the maximum speed of your engine. For that purpose, it becomes necessary to adjust the throttle controls on your lawnmower.

Throttle Adjustment on a Briggs and Stratton Lawnmower, step-by-step:

Here’s a step-by-step solution for adjusting the throttle on a Briggs and Stratton lawnmower engine:

● Step 1: Initial preparations:

– Safety measures:

Although the throttle adjustment is a relatively simple process that doesn’t involve extensive work, it is still better to take adequate precautionary measures before you begin anything. Take the spark plug cable out.

– Ready your equipment:

For this entire activity, you need a screwdriver, a 10mm wrench/socket, a feeler gauge (to measure clearance), and a pair of nose pliers. Make sure you have this equipment at your disposal.

● Step 2: Disassemble the parts to access the governor’s arm:

The governor’s arm is right next to your carburetor. To gain access to the governor’s arm, you need to detach individual components.

– Air filter:

The air filter is usually present at the exterior. It comprises an air filter housing inside which the filter is present. Take the housing off by unscrewing the bolts that connect it to the lower body.

– Fuel tank:

If your governor is accessible after removing the air filter, then you probably need to ignore this step. However, in some models, such as in Honda push behind lawnmowers, the fuel tank also needs to come off before you can see the governor’s arm. Just remove the bolts securing the tank. You don’t need to detach all the fuel lines that connect with the carburetor.

Now that you can see your governor’s arm, we shall now proceed towards adjusting its throttle lever.

● Step 3:  Measure the clearance before adjustment:

We want to determine how much clearance is present between the choke arm and the control lever when the throttle lever is at the fast position. For this purpose, we shall use a feeler gauge. Typically, it needs to be 1/40000 of an inch or 0.0006 mm.

If the clearance value is more than the required value, you need to tighten the throttle cable.

● Step 4: Throttle cable and lever adjustment:

The throttle for the engine can be adjusted by either adjusting the cable or the throttle lever.

– Cable adjustment:

To adjust the cable, use a 10mm wrench to loosen the nut and pull it back towards you. Then tighten the nut again and check if the clearance value falls short of 40,000 of an inch or not. After the required clearance is achieved, the cable doesn’t need any further adjustment.

– Governor arm adjustment:

Another way of fulfilling the same objective of throttle adjustment is to adjust the throttle arm’s position, also known as the governor’s arm. To do this, pull the choke lever on your mower handle to the ‘fast’ position.

After that, use a 10mm wrench to unscrew the nut that connects the governor’s arm. The arm is pivoted to the engine by a pin. After the nut is loosened, rotate the pin fully in the clockwise direction and tighten the nut on the governor’s arm again

– Caution:

The above procedure is pretty simple to do. However, there are a few things that need to be taken care of. Make sure that the choke lever is pressed to ‘fast’ position. While rotating the pin, use nose pliers. Ensure that the governor’s arm doesn’t move forward or backward during this rotation along with the pin. This misadjustment of the governor’s arm can be quite critical as the engine RPM might be raised to an alarming degree. Your engine can be harmed to a great degree if this condition happens.

● Step 5: Reassemble:

Now that your governor’s arm has been adjusted, reattach everything that has been pulled off. Restart your engine and observe the change in the engine speed with the modification carried out.

Related Questions:

1. What causes a lawnmower engine to rev up and down?

If your lawnmower engine is not running smoothly and goes into the surge, there can be various causes that lead to it. These are mentioned below:

– Airflow:

The cause of engine problems sometimes may be as simple as an airflow blockage. To troubleshoot this, check the air filter of your device and clean it from any debris. If the engine starts up again and runs without surging, then you need not do any further troubleshooting.

– Spark plug:

Sometimes, a defective or a loosely adjusted spark plug might be one of the reasons for your engine revving up and dying. To check this, first, see whether the spark plug cable is tight enough. Pull the plug out and see if the electrodes aren’t covered in deposits. Clean the electrodes using a wire or sandpaper if possible. Also, check its electrode gap using a spark plug gauge. The gap should be as prescribed in your engine’s operating manual. If it appears defective enough, replace it altogether with a new one.

– Carburetor:

If the spark plug replacement does not fix the issue, you need to clean the carburetor jets. When the fuel becomes stale, deposits begin to form in the carburetor jets. These deposits can restrict the fuel-air mixture’s flow to the engine that might result in the engine not running smooth. Apart from the cleaning, also ensure that the carburetor is adjusted correctly.

2. How do I increase the speed of my lawnmower?

Increasing the speed of your lawnmower engine can boost your cutting speed and thereby shorten your mowing hours. Following are the ways of speeding up your lawnmowers:

– Pulley size:

This step applies to riding lawnmowers. These engine pulleys are located underneath the mower. Increase the size of both the pulleys increases the maximum speed of the engine.

– Governor adjustment:

Governor governs the amount of fuel entering the engine for combustion. It sets an upper limit on the maximum speed of the engine. Governor adjustment can be performed by adjusting the arm, as shown in this blog post.

Another useful technique is to shorten the length of the spring connected to the arm. Shortening its length induces tension in the spring that can enable the governor to draw more fuel mix from the carburetor and increase your machine’s maximum speed.

– Air filter:

Keeping the air filter clean and debris free can ensure better engine performance. You can change the filter if it has become old or damaged.

– Engine oil:

Just like you keep your car well maintained by regular oil checks, using the right engine oil for your mower can also boost up your engine speed by providing superior lubrication between the contact surfaces of your engine. It is not a bad idea to use your car’s engine oil for your mower.

3. Why are lawnmowers so slow?

Lawnmowers that haven’t been appropriately maintained often run slow.

  • Clogging is the primary factor that could contribute to a loss of power. The clogging might be in the carburetor jets, fuel filter, or air filter. This clogging in the air filter is due to the dust in the environment. For carburetors, it owes to a low fuel quality resulting in debris deposits.
  • Fuel blend: Often, vehicles’ fuel is blended with ethanol for cost and environmental benefits. This fuel blend may not affect larger engines in automobiles. However, for small engines like lawnmowers, pressure washers, chainsaws, this fuel blend can cause a reduced engine performance. If you notice this performance drop, stop using this fuel, and purchase pure gasoline for your engine. The continuous use of this fuel might degrade your engine life altogether.

Final Remarks:

The throttle adjustment might add extra RPMs to the engine. However, one must be aware that the lawnmower engine must not be operated an RPM value higher than about 3000. You can purchase a digital non-contact tachometer if you intend to keep changing and measuring your engine’s RPMs. Also, keep your engine well maintained by timely servicing its carburetor and filters. It would be great if you also kept a check on the oil change every once a session. Also, don’t forget to replenish the fuel in your tank every once in a while. It is also a good idea to use a fuel stabilizer if you intend to store your lawnmower for a longer duration.

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