Kawasaki Mule SX: 9 Common Problems & Fixes!

Despite its often mentioned reliability, Kawasaki Mule SX still has mechanical problems and design faults recognized by its owners and professional reviewers. In this post, we’ll go through the most common issues and how to solve them.

1. Oil filler cap jumping

In Kawasaki Mule SX, the oil filling cap is found on the top of the engine valve cover. However, it jumps off, and soon after the engine starts, the oil starts to spewing out all across the engine bag, which is a pretty miserable situation.


The warranty claim is only valid if your vehicle is under warranty period. Nevertheless, any mechanic can help you sort this issue by cleaning the oil pressure relief valve hose line, which usually gets stuck by freezing moisture caused by exhaust gases diverting back to the engine. In such a situation, the pressure inside the valve cover will strictly hit the oil cap, causing oil to spew all over the engine.

2. Heat rising from under the seats

Many vehicle owners have experienced heat dissipation under the seats and warm air blowing behind the front seats, painful in the scorching season. The perforated air vents beneath the floor serve the purpose of unrestricted airflow towards the engine compartment, which soon becomes a very upsetting and hectic problem for the owners.


Interestingly, aftermarket heat shield kits are the most practical and cost-effective fixation to this cabin heat issue. For this reason, you can apply a heat-resistant (or heat insulation) sheet under the seat and the back of the seat with adhesive tape. This article presents the best insulation options for reducing heat (and noise).

You would need to take off the seat and bind the sheets to every possible air leaking spot.  Consequently, giving thought to this solution might hold back roughly 70-80% of the cabin’s heat.

3. Idling issue from carbon deposits

You would feel the engine stalling or idle poorly, like the engine would die, if you lift your feet off the pedal. The black soot (carbon deposits) gathers up inside the throttle body due to the reversion of hot exhaust gases to the engine’s top. In layman’s language, the throttle body is primarily responsible for any such abnormalities.


You can quickly fix the issue in a pocket-friendly manner if you are not under warranty. All you need to do is clean the throttle body whilst keeping the electronic sensors intact. You need to spray the residue dissolver (such as WD40) inside the throttle body and focus on cleaning while the full open and full close of throttle blades. In addition to this, you should also consider cleaning or replacing the oil filter if found dirty.

4. Gear shifting problems due to faulty design

Many people have complained about the jammed gear stick during downshifting and upshifting of the vehicle, which would be pretty annoying for the newer Mule SX models. You may experience when either shifting from Low (L) to High (H) or High (H) to Reverse (R).

Commonly, the vehicle owners instantaneously become anxious that the main transmission spinning gear might be hitting hard with other gear. However, there is no fault in the transmission mechanism. Concerned ones get their Mule SX to company dealerships, which is entirely normal for CVT Transmissions after the initial inspection.


This gearbox design is unquestionably the company’s fault. Even the company does not offer any recall or provides any solution. But we have found the simplest fix for this problem. It would be best to tap a little foot on the accelerator whilst uplifting or downshifting the gear. There will be no jam or jerky shifting anymore.

5. Loss of power

After some hundred hours, some owners noticed a decline in the acceleration and significant loss in power. Despite the fact, there was no evidence of a blockage in fuel lines, and even the fuel pump was working fine. Besides, the engine spark plugs were good also. This entire situation might make you feel stranded when your powerful Mule SX struggles to climb the hill, even in the Low (L) gear.


After discussing the issue with many owners who faced this problem, the faulty fuel lines and fuel filter seemed the guilty part as the lousy gasoline quality is responsible for the blockage of certain parts, which either need replacement or cleaning.

I would recommend replacing the fuel filter on top of that try flushing the fuel lines with SeaFoam. The solution does not require any special mechanical knowledge. And most of the people could easily follow the instructions to repair their Mule SX.

6. Rattling noise from the seat belt box

Upon investigation of this problem, we realized that the consistent rattling sound is coming from the seat belt box while driving off-road. It might be possible that Kawasaki recalls the vehicle to sort out this particular issue.


For now, there is only temporary fixation until the Kawasaki recall specific models. The solution is to replace the seat belt box with other aftermarket seat belt boxes to avoid any rattling and annoying sound.

7. Lack of Side Mirrors

Side mirrors and rear mirrors are necessary as per the federal regulations, requiring every motor vehicle to have rear reflectors (or rear mirrors). However, the Kawasaki Mule SX does not come with rear mirrors. Without having these rear reflectors, any driver would feel upset while driving.

Side mirrors are essential for the basic protection of the rider and pedestrians, and other motor vehicles on the road. However, this does not affect the off-road performance of the vehicle.


If you are experiencing any such problem, you can take your Mule SX to the mechanic and ask them to install aftermarket side mirrors, which you can buy online as low as $40/pair.

8. Electrical power loss

If the battery is problematic, you may encounter issues with your engine ignition. A bad battery’s symptoms can also occur as no dash lights or the engine starter not working correctly. If any of these happens, it means your vehicle’s battery needs to be diagnosed or replaced.

Such situations usually result from three possible factors; drained battery, loose battery terminals, or loose ground end with the body. An experienced mechanic can easily diagnose the issue within the first few minutes of inspection.


Make sure the battery terminals are clean and tight enough to avoid any sparking. If you find rust on terminals, give them treatment with wire brushing. Look out for the negative terminal, clean it and check that it is correctly grounded with the chassis. Do the same process with a positive terminal.

Still, if the engine does not get the ignition, try tracing the earth cable connected and going from the engine casing to somewhere on the frame. The problem is most familiar as the wire is more exposed to harsh road conditions such as mud and water. Suppose any of these does not work for you. Reach out to any mechanic for professional support.

9. Engine misfiring 

There are merely a few reasons behind the misfiring or sputtering of your Mule SX. As you know, Mule SX comes in two variants; one is having a carburetor and the second being electronically fuel injected. Both engine configurations may include a similar issue just because of vacuum or fuel leakage. In addition to this, corroded spark plugs are the main reason behind the sputtering in most cases.

Any malfunctioning spark plug connected with the cylinder will cause the engine to misfire, resulting in poor performance and sputtering. Therefore, it’s time to replace the spark plugs with factory-recommended ones.


Start the inspection of the spark plugs, remove them one-by-one and check for any corrosion or buildup. If you find any debris, make sure to eliminate any possible buildups using fine sandpaper. Never ignore if the point is having signs of wear and tear. After this, double-check that space is enough between the ground electrode and the middle end.

On the next step, remove and check carefully for the wires connected with spark plugs. Motorcycles and utility task vehicles have the exact ignition mechanism. Thus, over time, the threaded portion connecting with the spark plug will be rusted or corroded, hindering the required electric current for proper combustion.


To conclude, we have put our maximum effort to cover each possible problem and its solutions, which somehow made this article slightly lengthy.

Generally, not every Kawasaki Mule SX is going to confront such issues. As a matter of fact, everyone having Mule SX should have adequate familiarity with problem-causing engine and body components and methods on how to fix them.

I hope this article saves lots of your precious time and guides you thoroughly in fixing these issues, on your own or by a trusted mechanic.

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