There are quite a few reasons the Kawasaki Mule SX sits firmly near the top of the list of best cheap side-by-sides.
It’s hard to believe that a Kawasaki Mule is one of the lowest-priced utility vehicles in the industry, but this one is. And a review of the Mule SX shows explains why it’s looked at as such a good value.
But as you’ll see in that review, it’s not all sunshine and roses with the Mule SX.
These models offer a good many positive, but they are prone to seven common problems that frustrate owners including:
- Oil filler cap shooting off
- Oil leaks
- Constant bottoming out
- Rough ride from the suspension
- Gear shifter sticking
- Carburetor causes starting and running problems
- Loss of speed and acceleration
This guide will detail the causes and proven fixes for each of these issues.
For more detail on the quality of Mules as a whole, check out this guide to Kawasaki Mules’ main strengths and weaknesses.
Oil Cap Filler Popping Off
Many owners have reported that the oil filler cap, which is found on top of the engine valve cover, is prone to popping off resulting in oil spewing out across the engine making a mess, and more importantly, a fire hazard.
This happens as the breather tube can fill with moisture created by exhaust gas, and that moisture can then freeze causing a blockage in the tube.
The resulting build up of pressure can result in the oil fill cap shooting off.
The Mule Pro FXT suffers from this same issue, and there was even a recall on 2015-2020 FX, FXR, and FXT models as well as 2016-2020 DX and DXT because of it.
Fix
The fix was to install an oil catch can on all recalls, as well as most new models.
If your SX does not currently have an oil catch can installed, you should have one installed to prevent this issue.
Refer to your owner’s manual to see if this may be covered under warranty.
Oil Leaks
As mentioned above, newer model SX’s are fitted with an oil catch can as a remedy to the issue with the oil filler caps shooting off.
Under the oil catch can is a drain plug. This drain plug can fill with oil and then start to overflow, leaking out oil onto the ground under your Mule.
This can cause quite a mess on the floor where you store it and on the components near the engine.
Fix
This potential issue, and its fix, is even referenced now in the SX owner’s manual.
It states that there is a transparent drain plug at the bottom of the catch tank, and that if you start to see any oil and/or water accumulating in that drain plug, you need to remove the plug and empty it.
Checking this regularly will help to prevent any oil overflows.
Constant Bottoming Out
With the stock suspension system and the stock tires, the Mule SX only gets a maximum of 6.1 inches of ground clearance in the base model.
While some of the upgraded SX models offer up to 8.7 inches of ground clearance, you’ll find that these models will bottom out repeatedly when driving off-road.
This is especially true on rutted trails, and even smaller logs and rocks will cause the bottom of these models to scrape.
Now these models aren’t technically meant for serious off-road riding, but it can be pretty frustrating that they bottom out so easily even in easier off-road terrain.
If you’re looking for a Mule that’s a little more off-road capable, have a look at an overview of the Kawasaki Mule Pro MX or the Kawasaki Mule Pro FXT Ranch Edition.
Fix
If you’re eyeing a Mule SX and you plan to ride trails or off-road a good bit, it’s highly recommended to go with one of the upgraded models that offers 8+ inches of clearance.
But you can also look at adding bigger tires to increase the clearance, or upgrading the shocks to achieve the same result.
Check out the eleven most popular Kawasaki Mule accessories to see which aftermarket shocks give owners both an increase in ground clearance and a smoother ride off-road.
Rough Ride From The Suspension
This Mule SX is not meant to be an off-roading vehicle, and the stock suspension system confirms that.
It’s non-adjustable, offering only 3.1 inches of suspension travel in the front and rear and contributing to the poor ground clearance mentioned above.
If you’re driving at low speeds in easy to medium terrain like these models are intended to do, the suspension offers a pretty smooth and comfy ride.
But if you get out on the trail or onto any uneven terrain that’s anywhere close to rough, the ride will be quite jolting and uncomfortable.
Fix
With a non-adjustable suspension, the only real fix for this is to upgrade to some aftermarket shocks which will help to smoothen the ride and offer a bit more travel.
Mule SX Gear Shift Problems
The gear shifter is prone to sticking in these models, similar to the issue found in the Kawasaki Mule 4010 models.
This happens most often when you’re at a stop and attempting to switch into Reverse or Low, but can happen when making any shift.
You’ll find that you’ll have to put some real force behind the gear shift to get it to into the desired gear, which is annoying and worrisome.
This happens when the gears and collars within the gearbox/transmission don’t line up perfectly, preventing the gear shift from taking place.
Fix
By giving the Mule SX a little gas when this happens, the clutch should engage and slightly shift the transmission into place properly so the gears align correctly again, making for a smooth gear shift as intended.
So while the engine is running and you encounter this problem, give the engine just a slight bit of gas (around 100 RPMs) and then attempt to shift gears. This should unstick the gear shift and
enable you to move it to the desired gear.
If you have powered off while not in neutral, and you experience a stuck gear shift, hold down the brake and start your Mule in its current gear. You should be able to shift gears from there.
Have your foot near the brake when you do this as a precaution.
Carburetor Causes Starting & Running Problems
The cheapest Mule SX Base model is equipped with a carburetor rather than electronic fuel injection.
While carburetors do offer some advantages, they also lead to more issues including:
- Hard starting
- Engine refusing to start without choke
- Sputtering or stalling at idle
- Engine surges
These issues generally occur due to the carburetor’s tendency to clog and gum up over time from dust, debris, and other gunk that finds its way in from riding.
The two pilot jets in the carb are particularly prone to gumming up.
If these pilot jets become even partially clogged, the carburetor won’t fuel correctly and you’ll experience the Mule being hard to start in cold weather or hard to start any time without using the choke.
You may also experience sputtering and stalling while idling, and the engine surging with the inconsistency of the fueling.
Fixes
When you run into these symptoms with your Mule SX, the carburetor should be the first suspect of the cause.
You’ll want to thoroughly clean your carburetor using WD-40 Carburetor Cleaner, being sure to check and clean the pilot jets inside of it as well.
You’re going to need to remove and disassemble the carburetor in order to clean it properly, and your repair manual or Kawasaki’s website (or a number of YouTube videos) should be able to guide you in this.
Once you disassemble the carb, you’ll see the pilot jets within the fuel bowl. Remove and inspect both of them to ensure you can look through them completely and there is no clog.
Regardless, use a fine wire to unplug them and then spray through them with your carb cleaner afterwards.
A good cleaning and unclogging of the jets and carb should have you back to running and idling normally.
Loss of Speed and Acceleration
You may also experience a lack of speed, acceleration and overall power from your Mule SX after a certain number of hours of use.
While Kawasaki Mules aren’t known for their speed anyways, this will be quite noticeable when topping hills or hauling/towing heavy loads.
The most common cause of this the fuel filter clogging and leading to a failing fuel pump, which is also a common problem in the Kawasaki Mule Pro MX.
Inspect the fuel filter to see if it is turning a dirty brown color, which would indicate it is clogging and can lead to fuel delivery issues.
If your fuel filter remains clogged for an extended period, it can also lead to a lack of lubrication to the drive motor in the fuel pump and eventually ruin it.
If you hear a whining sound while riding, this indicates the fuel pump may be struggling.
Fix
Inspect your fuel filter regularly to make sure it’s not clogging. If it is, you may want to replace it with an upgraded unit to help prevent clogging and issues with the fuel pump down the line.
You can also add Sea Foam Motor Treatment to help flush the lines regularly and better lubricates your engine.
Engine Not Starting
Kawasaki engines are about as solid as they come, but even the best engines sometimes won’t start.
That’s true with the Mule SX’s engine in some cases, but is usually to do with one of the components that connects to it than the engine itself.
Some of the more common causes of the engine not starting are:
- Battery draining
- Loose battery cables
- Transmission not being in Neutral
- Spark plug fouling
Battery
The stock battery in Kawasaki Mules is solid, but nonetheless is prone to draining when not in use for extended periods.
It’s highly recommended that you hook your Mule battery up to the Battery Tender Pro if yours sits for more than a few days at at time.
This will help ensure the voltage is always at 12+ and your battery won’t be the cause of an annoying no-start.
The battery cables are another common culprit, so you should check to ensure that they are connected tightly in place.
Transmission Not In Neutral
This may seem like a silly one, but new owners may not be aware there is a safety switch that will prevent the Mule SX from starting if it’s not in Neutral (since there’s no Park setting).
If you simply hear a clicking noise when trying to start your engine, this could be your issue.
However, you can bypass this safety switch on the SX models by pressing down the brake pedal and starting it.
Spark Plug Fouling
Check your spark plugs for fouling, which will be indicated by the tips being burnt or a grayish color.
This can happen if you make a lot of short-duration trips, which are hard on spark plugs and the battery.
If you’ve got a fouled spark plug, your engine won’t get the spark it needs to start and you’ll need to replace it with an upgraded iridium spark plug.
Conclusion
Some of these issues are pretty nitpicky, but others can affect the operating ability of the Mule SX and be a real thorn in the side of owners.
Even so, Kawasaki Mules make for some of the best UTVs you can buy in all of the industry.
