Incorrect idle adjustment on your ATV can lead to all sorts of issues. If the idle is set too low, the engine may stall and struggle to stay running. On the other hand, an idle set too high causes premature drive belt wear, shifting may become difficult, and you may even experience unwanted vehicle movement.
Keep reading to learn how to get your ATV to idle correctly for optimal vehicle performance.
What Does It Mean When an ATV Is at Idle?
An ATV is running idle when the engine is turning slowly, at no load, with no throttle applied, and usually out of gear.
Too high idle is when the engine turns faster at idle than recommended (higher RPMs).
Too low idle is when the engine turns slower at isle than recommended (lower RPMs).
Please note that improper adjustment is just one of several possible causes when your ATV is idling too high or too low:
- Carburetor issues such as a vacuum leak, a clogged pilot jet, or the butterfly not closing.
- A blocked or dirty air filter.
- Dirty fuel filter.
- A stuck choke.
- Throttle cable issues such as connectors not seated, adjuster coming loose, or cable dragging inside the sleeve.
- Idle-bypass-valve is not operating correctly.
- Sensor issues such as a bad or loose throttle position sensor or a dirty mass-air sensor.
- Warm or cold weather – temperature affects how easily the fuel evaporates.
- Bad fuel
If you’re unable to get the idle to where you want it by adjustment only, these are the most common culprits. Troubleshooting and fixing these issues will be covered in a separate post.
What Is the Correct Idle Speed on an ATV?
The correct engine speed an ATV should idle at varies, but most ATVs should idle somewhere between 1100 to 1700 RPM.
Engine size, year of manufacturing, brand, carb style, and whether it’s a two-stroke or four-stroke are all factors that play a role when determining the correct idle speed.
Please refer to the owner’s manual for your specific ATV’s exact engine idle speed.
How to Adjust the Idle on an ATV
The idle adjustment is not the same in all ATVs. Some bikes, typically budget models or older ATVs, can be easily adjusted at home. Newer and more advanced models may require help from a trained mechanic with access to special tools.
- On a carbureted ATV, the idle is adjusted by turning the throttle adjustment screw located on the carburetor housing.
- On ATVs with a mechanical throttle cable, the idle can be adjusted by adjusting the throttle cable. This applies to most ATVs with a conventional carburetor and some fuel-injected models.
- On fuel-injected ATVs with an electrically controlled throttle (drive-by-wire), the idle is governed by the electric control module (ECM). The idle is not adjustable on these bikes unless you use an aftermarket tuner.
Adjusting the Idle on a Carbureted ATV
Follow the steps below to adjust the idle on a carbureted ATV by adjusting the idle screw.
Step 1: Drive the ATV for 10 minutes, allowing the engine to warm up
The engine needs to be at operating temperature to adjust the idle properly. Adjusting the idle when the idle is cold can lead to poor idling when the engine warms up.
Some ATVs are designed to run at a slightly higher idle when the engine is cold before it settles down automatically after a few minutes when the engine has had time to warm up. Adjusting the idle in the cold-start phase will cause the idle to drop too low when the engine heats up.
Step 2: Locate the idle screw on the carburetor
The idle adjustment screw is located on the carburetor. On most ATVs, the carb is readily accessible, but you may need to remove a plastic cover on some models.
The adjustment screw is usually on either side, but it can also be at the front of the carb. Look for a brass-colored screw designed to be adjusted with a Phillips or flat-head screwdriver.
Reaching the screw with the screwdriver may be a bit fiddly. It helps to identify the best access angle and have the correct length screwdriver before you begin the actual adjustment.
Step 3: Take note of the current engine idle speed (RPM)
To know if the idle needs adjusting, whether it needs to be changed up or down, or when you’ve achieved the correct idle, you need a way of determining the engine RPMs (Revolutions Per Minute).
Here are three different methods you can use to determine the idle speed:
- Read the RPMs in the ATVs instrument panel. If your ATV has an analog or digital instrument panel, it may have an option to display the engine RPMs. You may need to toggle through the various display modes on a digital instrument panel to get to the RPM mode.
- Install an aftermarket tachometer. Consider installing an aftermarket tachometer gauge if your ATV does not come with a factory tachometer (the instrument that reads RPM). The meter connects to the ignition and coil to read the current real-time RPM. Note that this is a job that requires mechanical skills slightly above average.
- Determine proper idle speed by ear. However, not as accurate as a tachometer, this method will work just fine most of the time. With some experience, you’ll be able to tell by just listening carefully if the idle sounds a bit off.
Step 4: Turning the idle screw to adjust the idle
Adjust the idle by turning the idle screw in or out depending on whether you’re looking to raise or lower the idle:
- Turning the idle screw in (clockwise) increases the idle RPM (higher).
- Turning the idle screw out (counterclockwise) decreases the idle RPM (lower).
If your ATV has a tachometer, turn the screw slowly until the gauge displays the correct RPM specified by the manufacturer.
If you’re adjusting by ear, turn the screw slowly clockwise until you begin hearing signs of engine stalling, such as popping or stuttering. As soon as these symptoms occur, turn the idle adjustment screw half a turn clockwise to increase the RPM slightly. The engine should now be idling smoothly with no signs of stopping.
Adjusting the Idle on an ATV With a Throttle Cable
This is how you adjust the idle on an ATV with an adjustable throttle cable. The same steps apply whether the ATV is carbureted or fuel injected.
Step 1: Bring the ATV to operating temperature
Any time you’re making adjustments that affect idling, you need to ensure the engine is at operating temperature for the best results. Please refer to step 1 above.
Step 2: Locate the throttle cable adjuster
Older ATVs, budget-friendly models, and most youth ATVs use a mechanical steel cable to transfer movement from the thumb throttle and down to the carburetor. The cable should move freely inside a protective sleeve that s held in place at both ends.
You’ll find an adjustment mechanism at either end of the throttle cable assembly. When adjusted, it will affect the bike’s idle.
On most ATVs with a throttle cable, the adjuster is located up by the thumb throttle, usually covered by a rubber grommet.
Step 3: Pull back the protective rubber grommet
Pull back the rubber grommet by hand to reveal the adjustment mechanism. You may need to use a screwdriver to pry the rubber back in some cases.
Step 4: Loosen the locking nut
A locking nut, also called a jam-nut, secures the adjustment screw. When tightened, this nut prevents the adjustment screw from unwanted movement.
Usually, the locking nut can be loosened by hand. Alternatively, you need to use the correct size wrench to get it loose.
Bring the locking nut a few rounds of thread back to allow free movement in the locking nut.
Step 5: Make the required adjustments to the adjustment screw
Just as when adjusting the idle by making adjustments directly to the idle screw located on the carburetor, you need to know whether the idle is too low or too high and when it’s adjusted properly.
Please refer to step 3 above to learn how to read the bike’s RPM.
Adjusting the idle up or down is done by turning the adjustment screw or sleeve clockwise or anti-clockwise.
- Turn the adjustment screw clockwise or up to increase the engine idle speed.
- Turn the adjustment screw anti-clockwise or down to decrease the engine idle speed.
Keep turning the screw until you reach the desired engine idle speed.
Step 6: Fasten the locking nut and reinstall the rubber grommet
Now that your idle is appropriately adjusted, you need to ensure the adjustment screw stays in place by tightening the locking nut back up.
Grab the adjustment screw with one hand and keep it from moving as you tighten the locking nut firmly with your other hand.
Adjusting the Idle on a Fuel-Injected ATV
The idle on a fuel-injected ATV is set by the ECU module, automatically adjusting the fuel-air mixture. Unless you get an- aftermarket tuner box, there is no way of making adjustments to the idle.
Please note that manipulating the ECU with a tuner requires special mechanical knowledge and experience and is something you shouldn’t attempt unless you know what you are doing.
When the idle is not right on a fuel-injected ATV, most of the time, the problem is caused by a mechanical issue, as listed initially in this post.
Which Way Do You Turn the Idle Screw on an ATV?
When adjusting the idle on an ATV, the idle screw should be turned clockwise (in) to increase engine idle speed or anti-clockwise (out) to decrease engine idle speed.
Related: ATV Won’t Stay Running or Won’t Idle