5 Common Problems with Kubota Kx121-3 (Solutions Included)

Kubota is a trusted industry leader in the small excavator sector. This tiny excavator from Kubota, the KX121-3, is not only reliable and versatile, but it also packs a lot of punch. Excavators manufactured by Kubota are renowned for their durability, lifespan, and productivity.

However, the KX121-3 is not fully problem-free. Problems with the hydraulics, fuel delivery, engine overheating, and transmission are all too prevalent and may put you in difficulty.

Towards the conclusion of this article, I’ll discuss five common issues that arise with the Kubota excavator KX121-3 and how to resolve them in a snap. Let’s start with a short review of the summary table.

Problems and Solutions at a Glance:

Problems with Kubota KX121-3Solutions
1. Fuel Delivery ProblemReplace injection pump
2. Excavator Hydraulic thumb ProblemCheck thumb cylinder, thumb valve; clean or replace them.
3. Bogging And Stalling IssueCheck fuel and add necessary; Purge the fuel system;
4. Excavator Won’t Start, Just Clicks  Check battery and motor connections; Keep secure and clean.
5. KX121-3 Engine may be overheating.  Flush the whole coolant system and replace as necessary.

5 Common Problems with Kubota Kx121-3 and Their Possible Solutions:

You may experience Kubota KX121-3 problems due to many reasons. Here are some of the reasons and how to solve them.

1. Fuel Delivery Problem

This Kubota KX121-3 super series mini excavator will be equipped with a cutting head. Potentially, this might create a problem with the way fuel is being delivered.

Perhaps the problem originates with the injectors or the injection pump. Black smoke may be an indication of this problem.

The fuel rack wear due to the bent ‘apparatus’ (which is a component of the injection pump) is perhaps the root cause of this issue.

The Fix:

Take out the injection pump, then search for “apparatus.” This problem will most likely be solved by new apparatus installed within the fuel injection pump.

When necessary, the worn fuel rack needs to be replaced with a new one.

This problem can be resolved entirely by replacing the damaged injection pump with a brand-new in its place.

2. Excavator Hydraulic Thumb Problem

This is a common problem on the Kubota Mini Excavators. If you have a thumb attachment, or even if you don’t, you need to make sure your thumb control valve is set in neutral when it’s not being used.

If this is not done, they will actually wear down your hydraulic cylinders on the excavator and eventually it will lead to hydraulic cylinder failure.

The thumb control valve works off of the main hydraulic pump so when its activated, it pulls from the main pump which is what causes that added wear and tear on your cylinders.

The Fix:

Examine the thumb valves on the Kubota KX 121-3 excavator to make sure they are not jammed or binding.

For the Kubota KX 121-3 excavator, make sure the hydraulic pumps and tanks have pressure release valves.

Check the Kubota excavator KX 121-3 for oil leaks and air in the system.

Inspect the thumb cylinder of the Kubota excavator for leaks, corrosion, and binding of the cylinder rods.

3. Bogging and Stalling Issue

Many customers have reported bogging and stalling problems with their Kubota KX 121-3.

There have been reports of this problem occurring for customers after the excavator had been sitting idle for several days. When the vehicle was started, it began to bog down and sounded as if the engine was ready to die.

When attempting to start the machine, it sputters and stalls. It makes no difference whether the machine is at idle, under no load, or with the throttle at halfway. It will run flawlessly, then abruptly begin to miss, sputter, shake, and then almost die; puffs of black/white smoke will emit from the exhaust.

After a few seconds or sometimes up to two or three minutes of flawless operation, it will stutter again. The sound of the fuel pump is consistent; it does not appear to slow down or speed up.

The Fix:

The bogging and stalling problem is typically caused by a lack of fuel, poor quality fuel, or too much engine oil.

  • Check the level of fuel and add more if needed.
  • If necessary, the fuel system should be purged.
  • Always be sure you use fuel of a high quality.
  • Drain engine oil to prescribed oil level.

4. Excavator Won’t Start, Just Clicks

the Kubota excavator have issues with starting. Some users have faced clicking issue with their machine. All lights flash and relays keep clicking when trying to start, when turned to start you may hear a loud buzzing noise.

If your Kubota excavator won’t start, it could be due to the following:

Dead battery, corroded battery terminals, loose battery connection, faulty safety switches, bad starter motor, starter solenoid, bad starter relay in fuel lines, failing fuel pump, bad fuel quality, overheating engine, clogged fuel filter or fuel lines.

The Fix:

 There may be problems with the batteries. Make sure that the battery and motor connections are all secure and clean.

Battery life and voltage should be checked, and if necessary, new batteries should be installed.

Perhaps the cylinder is not receiving fuel. It’s important to double-check the fuel level, as well as the fuel shutdown valve and fuel filter.

5. KX121-3 Engine May Be Overheating

The water pump seals can be a cause for overheating. If the seal is leaking coolant internally the coolant will be pumped out of the engine and not circulated back into the radiator.

This can result in an engine operating temperature that is too hot for normal operation.

Also, if the seal is leaking externally this will also cause a problem with a loss of coolant from the cooling system.

The Fix:

 Reduce the weight or shift to a lower gear.

Check the coolant level to determine if it needs to be replenished, then inspect the hoses and radiator for leaks or other potential problems.

Any blockage in the coolant system might be the cause of the problem. The best course of action is to clean the whole coolant system and replenish if necessary.

It’s possible that the fan belt is broken or has come untied. Checking for wear and replacing as needed should be simple.

Perhaps all that’s needed is a good cleaning of the radiator core or screens to get things back to normal.

What Majority of the Users Feel?

The KX121-3 compact excavator is a popular among professional operators and people who require it to maintain their property. Small enough to be handled and maneuvered with ease, yet robust enough to dig into thick soil.

According to one user, they are well-balanced and have strong hydraulics; the only flaw, in his opinion, is the tinny travel pedals.

Aside from a few bugs, owners of the Kubota KX121-3 are pleased with the performance of their excavator. There are numerous websites and message boards where users have posted glowing praise.

According to another person, he has been using it for the past seven years without any complaints. In his opinion, everything has always worked as promised. The size and the controls are not an issue for him. he believes The angle blade is fantastic as well.

Finding the right product for your needs might be easier if you consider the feedback other customers have provided about it in the form of comments and reviews.

Frequently Asked Questions

What Replaced The Kubota KX121-3?

KX040-4 Compact Excavator.

How Much Does A Kubota KX121-3 Weight?

9063 lbs.

What Is The Difference Between Kubota U And KX Series?

The excavators of the KX series use a traditional tail swing, whereas those in the U series have a zero-tail swing arrangement.

How Many Horsepower Is A Kubota KX121-3?
42 hp (31 kw).

Final Thoughts

I have covered all of the most frequent issues that people have with their Kubota KX121-3 excavators. If any of these problems are bothering you, implement the fixes I’ve outlined.

If you want to avoid issues like these in the future, it is strongly recommended that you do routine maintenance on your excavator.

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