Kayo Fox 70 Problems (5 Most Common & Fixes)

Affiliate Disclosure:
As an Amazon Associate, I earn from qualifying purchases at no additional cost to you. Thank you for supporting my site.

The Kayo Fox 70 is quickly becoming a favorite among parents looking to give younger riders an early taste of off-road life and ranks as one of the best mini four wheelers for this year.

Boasting a number of safety features along with enough speed to give riders a thrill, this vehicle finds a good middle ground between safety and fun. 

And at a much less expensive price than most competitive models like the Yamaha Raptor 90 or the Polaris Outlaw 100.

But despite the many positives with this vehicle, a full review of the Kayo Fox 70 confirms that these models suffer from a number of common Kayo Fox 70 problems including:

  • Faulty carburetor
  • The chain popping off
  • Lack of low-end power
  • The brakes failing over time
  • The engine not starting or hard starting

This guide will detail each problem along with proven ways to prevent and fix them. We’ll also detail some of the highest recommended upgrades for the Kayo Fox 70.

In a review of Kayo ATVs in general, you’ll see that a few of these problems flare up in more than just the Fox 70.

Faulty Carburetor

By far the most common problem encountered with the Kayo Fox 70 is with the factory carburetor. 

Unfortunately, these carburetors are responsible for a number of recurring issues with the ATV including stalling, bogging down, rough idling, and the top speed eventually falling off. 

There are a couple of ways to overcome this.


Upgrade the Carburetor

The best way to overcome this issue is simply to replace this faulty factory carburetor.  Luckily, this is a fairly simple and inexpensive fix. 

A replacement carburetor can be purchased on Amazon for between $20 and $40.  The PZ19 ATV Carburetor is the most highly recommended, but technically any 19 mm carburetor will do.  

If experiencing any of the symptoms of this faulty carburetor listed above, installing an upgraded unit should have your machine back to running smoothly immediately.

Adjust the Idle on The Carburetor

If you’d prefer to attempt to fix the factory carburetor rather than replacing it, this can also be done. 

You’ll need to locate the idle adjustment screw on the right side of the quad.  This adjustment screw is located within a brass fitting and covered by a black rubber cap that fits over top.

Pop out the rubber cap to expose the flathead adjustment screw within the brass fitting.  You can completely remove the brass fitting using a pair of pliers to gain better access to the screw if need be. 

Using a small flathead screwdriver, back the adjustment screw out a couple of turns to loosen it.  Reinstall the brass fitting.

You may need to adjust it a few times until you find the proper setting, but increasing the idle by loosening this adjustment screw should help to alleviate some of the symptoms caused by the faulty factory carburetor.

The Kayo Fox 70 may not idle or even run properly until one of these actions is taken.

Chain Popping Off

The chain on the Kayo Fox 70 is generally installed a little too loose and has a tendency to pop off of the sprockets when hitting a bump in the road or riding in choppy terrain.


To fix this issue, owners will need to tighten the chain by adjusting the rear axle. 

To do this, first remove the chain cover by loosening the bolt that holds it in place.  Then, loosen the four bolts that hold the rear axle in place along with the two small jam nuts at the very rear that serve the same purpose.  

Once these have been loosened, you should be able to adjust the axle by pulling it back towards the rear of the machine.  This will create more space in between the front and rear sprockets while also serving to tighten the chain.

When you are satisfied with the adjustment to the axle and increased tightness with the chain, tighten the four bolts and two jam nuts to lock it in place and reinstall the chain cover.  You will likely need someone to assist you with this process.

MORE: Kayo Fox 70 Review, Specs, Pros & Cons

Lack of Low End Power

As the Kayo Fox 70 is designed for beginners, it does not have much low end power out of the box.

Many owners are disappointed to find that their machines will barely make it up low grade hills with small children driving, many times not having the power to get there. 

This makes the little quad almost impossible to ride on any terrain that isn’t flat and smooth.

Aside from the issues caused by the carburetor, this is the second most complained about aspect of the Fox 70. Fortunately, it’s fairly simple to overcome.


This issue can be fixed by replacing the sprocket(s) to provide more power, or by simply adjusting the idle via the throttle stop.

Replacing the Sprockets

A common process for adjusting speed and power in machines with chains, such as ATVs and motorcycles, is to replace the front and rear sprockets.  But there is a tradeoff among top speed and acceleration with this process.  

Making a change to a smaller rear sprocket and bigger front sprocket will increase the top speed of the vehicle, but decrease the acceleration.  Conversely, switching to a bigger rear sprocket and smaller front sprocket will increase the acceleration of the vehicle, but decrease the top speed.

In the case of the Kayo Fox 70, owners will want to increase the acceleration by replacing the front sprocket with a smaller one. 

The stock front sprocket is a 13-tooth sprocket. Many owners have had success moving to a twelve-tooth, eleven-tooth, or ten-tooth sprocket.

When doing this, you likely don’t need to mess with the rear sprocket in the case of the Kayo Fox 70 as it is more complicated than replacing the front sprocket, and simply replacing the front should give it enough added power to overcome this issue. 

With this fix, your kids should have no problem making it up hills and doing some light off-roading.  And the effect on the top end speed won’t be enough that they can’t still open it up for a thrill when they want.

Adjusting The Throttle Limiter

The easiest way to increase the speed, acceleration and power in the Kayo Fox 70 is to adjust the throttle limiter safety feature that restricts all of this initially. 

On the back of the throttle box of these ATVs, there is an adjustable bull nose screw.  This is your throttle limiter, and they come fully tightened out of the box.

To adjust the throttle limiter, twist this screw counter clockwise to unscrew it some.  You may need to use pliers to do this. 

The more you unscrew this, the more play the throttle will have, which will give you the full range of speed, acceleration, and power that this machine is meant to have. 

Once you’ve unscrewed this to a satisfactory position, tighten the nut to hold it in place.

MORE: Kayo Bull 200 Review – Top Speed, Specs, Pros & Cons

Brakes Failing Over Time

The hydraulic disc brakes in the Kayo Fox 70 are prone to failing after some time riding.

Obviously this is a problem with one of the top priorities of a youth ATV model being safety and with these models aimed at youth as young as six who are likely not experienced riders.

If the brakes go, you’ll know it right away as your kiddo will go to squeeze the brake lever it will be completely soft with no braking action.

Fortunately this tends to happen to one of either the front or rear brakes, and not both at a time, so there isn’t a complete loss of braking.  But that’s not to say it can’t or won’t happen.

Most of the time this happens for one of two reasons.  Either the brake fluid gets low, or an air pocket forms in the brake fluid reservoir causing the brakes to fail.


To fix this, if your brake fluid appears low you should start by refilling it and seeing if that does the trick.  If it doesn’t, you can be pretty sure you’ve got an air pocket.

You’ll need to either manually breed the brakes, or bleed them using a vacuum pump to remove the air pocket.

Doing so should restore braking power to the brake levers.

Engine Won’t Start

A number of owners of the Kayo Fox 70 have reported experiencing the engine not starting at some point.  This is likely due in part to one of the following:

  • Terminals/Wiring
  • Battery
  • Valves
  • Spark Plugs



A good place to start inspecting if the engine won’t start are the battery terminals.  Ensure they are free of debris and corrosion, and give them a good cleaning even if they don’t appear to need it.  Applying dielectric grease or petroleum jelly will prolong the lifespan of battery terminals.

Next, check the grounding wires connected to the battery.  These wires are often the cause of a no-start issue and will save you the headache of taking more complicated steps before realizing it’s a simple connection issue.


The stock batteries in the Kayo Fox 70 have a tendency to drain rather quickly.  If your machine won’t start, you can test the battery to ensure it is getting the intended 12 volts.  If not, you can try recharging it.

Hooking the battery up to a battery tender when the machine is not in use should help to prolong the life of the stock battery in the Kayo Fox 70.


Some starting issues with the Kayo Fox 70 stem from the intake or exhaust valves.  The most common occurrence is that these valves tighten too much creating an issue, but they can loosen as well. 

Both tightening and loosening affects your valve clearance, which if not maintained at the proper level, can result in your machine not starting.

The proper valve clearances can be found in the owner’s manual.  Check to ensure both valves are set at their proper clearances, and make the proper adjustments if not.

Spark Plug

Check the spark plug to ensure it is not coated with a foreign substance such as fuel, oil, or coolant.  You can also inspect the color to ensure the tip looks normal and does not appear burnt which would indicate fouling.

If the spark plug appears to be fouled, that is most likely your issue and you should replace it.  Replacing it with a high quality iridium spark plug is recommended.

Kayo Fox 70 Upgrades

To overcome some of these issues, or simply to ensure their Kayo Fox 70 runs better, owners may want to make any number of upgrades. Below are some of the most popular upgrades for this model.

Kayo Fox 70 Carburetor Upgrades:

Kayo Fox 70 Sprocket Upgrades:

Kayo Fox 70 Air Filter Upgrade:

Final Thoughts

While the Kayo Fox 70 makes an excellent choice for younger ATV riders, it is important for owners to understand that they may encounter some of the common problems with this machine such as a faulty carburetor, the chain popping off, lack of low end power, and the engine not starting.

That said, for many owners the tradeoff in dealing with some minor issues they may need to troubleshoot themselves is worth it considering they’re paying half the price they would for a model from one of the bigger names in the industry.

For more youth models, check out the following guides before you go: