When your engine revs too quickly in neutral, your ATV can idle high. This is also known as rough idling. Your ATV will sound louder and could begin shaking, which can make controlling your vehicle difficult. Why is your ATV idling high?
ATVs idle high for these reasons:
- Idle screw is mispositioned
- Outdoor temperature changes
- Stuck choke
- Pilot jet back-ups
- Poor-quality fuel
- Vacuum leaks
- Dirty air filters
This guide to ATV idling troubleshooting will go through each of the above causes of high idling in detail. We’ll also explain how to fix them so you can have better control of your ATV every time you ride. Keep reading!
7 Potential Causes of ATV High Idling and How to Fix Them
The Idle Screw Is Mispositioned
Your ATV has a component called the idle screw. The idle screw is also known as the air-fuel mixture screw because it determines the amount of air that’s allowed to combine with fuel.
Since it’s attached to the carburetor, when you tinker with the idle screw, you can increase the speed of idling. Your engine might run more smoothly as well depending on which position the idle screw is set to.
If you’re comfortable with it, then we recommend accessing the idle screw and checking its positioning. Try repositioning it and seeing if your high idling problem stops.
You can always bring your ATV to a mechanic and ask them to reset the idle screw.
If this solves your high idling problem, then great! This is one of the easier fixes, and it shouldn’t be very expensive either.
That said, if your ATV is still idling high even once you’re sure the idle screw is set into position, you still have plenty more areas you can troubleshoot.
Outdoor Temperature Changes
Here’s something we bet you never thought influenced the idling of your ATV (but absolutely does): the weather.
In the summertime when the temperatures and humidity are high, fuel vaporizes faster and more easily. This allows your engine to turn over effortlessly, reducing the rate of high idling.
When the days become shorter and colder, the fuel is not so thin anymore. As fuel thickens up, the engine strains more and idles as a result.
If you only have high idling issues with your ATV in the winter, then it could be that nothing is wrong with your vehicle at all. It’s just that high idling will occur more because of the cold temperatures.
Wait for warmer days and see if the issue abates. If it does, then there’s nothing wrong with your ATV, per se.
However, if your ATV high idles no matter the season, then you need to keep troubleshooting. Something is obviously wrong.
The Choke is Stuck
Your ATV’s throttle cable or choke is the next area to investigate.
When the choke gets stuck, the rate of air that’s allowed to enter the fuel mixture increases. This makes the fuel mixture leaner than usual and thus will cause a higher idle compared to a less lean mixture.
The throttle cable is located on the handlebars of your ATV, so use a screwdriver or a locknut to access the choke.
The position can get stuck. You’ll know that’s the problem if the idle screw and side plunger of the carburetor are separated from one another.
The side plunger is supposed to rest on the idle screw. Place these parts in the correct position, replace the handlebars, and try your ATV. Your high idling problem may be behind you.
If not, then it’s a good idea to lubricate the choke. You can use penetrating oil for this. Then take a pair of pliers and adjust the cable. If it’s been stuck for too long, your manual movement will help it stay in place.
That should hopefully do the trick provided the issue is with the throttle cable.
The Pilot Jet Is Backed Up
The pilot jet is a component of your ATV that receives the air-fuel mixture and then sets your ATV from idle to throttle between 15 and 20 percent. When your ATV sits idling, it’s the pilot jet that sends fuel to the engine.
When the pilot jet has issues, that negatively impacts the amount of fuel that reaches your engine. The fuel mixture becomes leaner and, you already know by now that that makes your ATV idle high.
Pilot jets are incredibly small components, so while you can try cleaning them yourself, this can be more difficult than you might initially assume. Feel free to let your mechanic take care of the job so you can ensure the pilot jets are clean.
You’re Using Low-Quality Fuel
If you want your ATV to run well, whether that’s to prevent high idling or backfiring, then you have to use high-quality fuel.
Yes, you will have to spend more money for better fuel quality, but it’s worth it. Your engine will run as smooth as butter and any idling issues should only be due to temperature changes, not your ATV itself.
Of course, even high-quality fuel can become a problem if you leave it in your tank for too long. Always drain your gas tank at the end of an active season.
If you plan on taking a two or three-month break from riding your ATV, then get rid of the leftover fuel.
When fuel becomes gunky, it can get stuck and lead to backfiring. It also won’t do your high idling problem any favors.
Here’s another potentially major contributing factor to your ATV’s high idle problem. The engine and the carburetor share between them a seal. When that seal is cracked, even a teeny-tiny bit, then you have a problem.
Air can now enter this area, affecting the consistency of the fuel mixture. As has been the case with so many other issues we’ve described, the fuel mixture becomes too lean, and your ATV will idle high.
You may notice that besides the high idling problem, you have a harder time maintaining control of your ATV because it’s just so jerky.
The next time you park your ATV, give the intake system a thorough look. You might not always be able to see any damage, but if you can, that’s your culprit right there.
You can buy a vacuum tester to determine if air is leaking. Should the tester results come back clean, then it’s time to check the carb itself as well as the manifold. These areas could be damaged. If so, leaks can still occur.
Perhaps you think a vacuum leak could be the problem but you’re not completely sure. In that case, it’s best to take your ATV to a mechanic. They can diagnose the issue and recommend a repair or replacement that ought to help.
The Air Filter Is Dirty
We discussed your ATV’s air filter in our article about ATV backfiring. If you missed that, we’ll provide a recap for you here.
Your ATV has an air filter that catches particles and contaminants. The only air that makes it to the engine should be clean.
Like the filter in your air conditioner that can probably use a change, your ATV’s air filter becomes less effective the longer it’s in your vehicle. You need to change it every couple of months or at least check it to determine if it’s dirty.
This small switch could be all it takes to stop your ATV from idling high.
Does your ATV idle high? In some instances, this could be a normal occurrence, at least if the high idling is very short-lived. Cold weather can also cause high idling.
Any other source of high idling is not something you want to ignore. The problem indicates issues with the carburetor, air filters, choke, or pilot jet. These parts could be dirty or damaged, and sometimes, you might even find a leak in critical places.
The good news is that fixing a high idle is doable on your own if you know the parts of your ATV well. You’re always free to take your vehicle to a mechanic for a professional diagnosis as well!