Kubota Servicing 101: Part 1 – Air Filter

First day of fall. The shelter belts are thinning, leaves yellow and the air is a bit crisp in the morning. Winter is on the horizon! With that in mind, let’s take a look at a couple of important fall service requirements for our Kubota tractor, and let’s do it today before there is a foot of snow on the ground.

If you haven’t discovered it yet, that little orange Kubota tractor of yours can take a lot of service neglect and still perform remarkably well. I’ve seen tractors here in the service department with fuel filters crammed with crud, the air filters caked with dust and seed and radiators with little more than creek water and mud in them. I am always amazed that in spite of that, these Kubota tractors keep starting and running. A testament to their superb engineering and design, regardless of age. That being said, we all know that our favorite orange tractor does need love every now and then, so with that, this article is the first in a multi-article set that covers basic Kubota servicing.

Small But Important
The single most important service item for your Kubota is the air filter. Diesel engines consume major amounts of air and all of it passes through that paper and mesh filter, so it has to be clean.

Remove air box end cap

Remove air box end cap

Locate the air box, and remove the snap on end cap. Inside the end cap you will see a silver “cup”. It’s inside here that you’ll find the first of what is usually a pile of dirt, bugs and debris. Strangely enough most owners don’t even realize that this cup is itself a filtering system, and subsequently, this area can be overlooked. Tap out the dirt and then replace the cup inside the end cap.

Clear out bugs and debris here - we've already clears ours in this picture

Clear out bugs and debris here - we've already clears ours in this picture

Next, remove the air filter element paying careful attention to the rubber rimed washer on the end of the wing nut. This 10 cent item has been the cause of more than one engine failure over the years. That rubber rimmed washer must be in perfect shape when it seals to the metal end of the air filter, otherwise all the dirt that you saw inside the silver cup gets ingested right into the engine, bypassing all the filtering! Assuming it checks out OK, remove the air filter element.

Make sure this washer seals against the filter snugly

Make sure this washer seals against the filter snugly

Cyclonic Action
Kubota engines employ cyclonic air filtration on all their diesels and for good reason – the air flows around the filter at high speeds, shaking out heavier particles (sending them to the silver cup we looked at earlier) and then filtering the finer particles through the medium of the filter before intake into the air plenum.

Rap the filter lightly on the work bench to dislodge any heavy particles, and then with a blow gun and care (under 30 PSI), blow out the element. It’s also acceptable to wash the paper element out in a bucket of warm water, rinsing back and forth until the paper is clean. Don’t blow air over it after washing, just let it stand and dry before reinstalling.

A Common Misconception
Everyone seems to think that you have to replace the air filter every year. Not so. With frequent cleaning and blowing out (minimum twice per operating season), you’ll get five years or better from that Kubota cartridge. Now you know why that Kubota brand filter is $37 and the NAPA one is $18.

Our cleaned up filter

Our cleaned up filter

OK, the filter is clean, lets inspect the paper for any breaks or tears. Use a Mag light or a small fluorescent trouble light and really look that element over. The slightest break in the paper and it’s garbage. Don’t cheap out here! There are things you can skimp on,and this air filter is not one of them.

Before reinstalling the filter, take a shop rag and wipe out the inside of the air canister assembly. Reinstall the element using the wing nut and rubber rimed washer, snap the cap and debris cup back on – we’re finished here.

Summary for Servicing your Air Filter

  • locate the air box
  • remove the push-on cap at the end of the air box
  • inspect and clean out silver cup on the inside of the air box cap
  • inspect washer and wingnut assembly for fit against metal base of air filter
  • remove filter cartridge and clean with light air pressure or warm water letting stand to dry
  • inspect filter for tears with fluorescent light if available
  • clean out air box assembly
  • reassemble filter, washer, wingnut, cup and cap

If you’d like to learn more, head on over to Part 2.

Service Department Vic

Related Articles
Kubota Servicing 101: Part 2 – Fuel Filter
Kubota Servicing 101: Part 3 – Cooling System
Kubota Servicing 101: Part 4 – Oil Change
Getting to Know your Kubota’s Clutch
Forum: Service, Repair & Maintenance


  1. Geoffrey Said,

    November 10, 2008 @ 2:33 am

    Hi, I am on the process of buying a second hand farm tractor and after reading your articles I’ve finally decided to get a kubota brand, I’ve read your articles and learn alot from it. But never find any regarding TIPS and things to consider on buying a second hand tractor. Could you be kind enough to teach me some pointers, thanks in advance and more power!


  2. Vic Said,

    November 12, 2008 @ 7:57 pm

    Hi Geoffrey, We’re going to be covering that off in an upcomming 2 part post, but we’re happy to give you the “readers digest” version today! The most significant tip we can give you when it comes to buying a second hand tractor, regardless of manufacturer is this: If the tractor looks like crap, it is. Period.

    A well cared for tractor looks like a well cared for car. It’s shiny and clean, the engine is bright, the tires are puffed up, the oil is clean, the owner is a fountain of information, knows every feature, when it was last serviced and is enthusiastic and engaging. A tractor that looks like it’s been left out in the rain since the Allies landed at Normandy, has an engine that looks like a grease lump or has even one piece of haywire holding something together should tell you to steer clear.

    The Kubota brand is known as the “gold standard” of the compact diesel tractor industry. Regardless of this, poor previous or current owner maintenance practices can greatly diminish the value of the tractor in terms of dollars and performance, even if it’s a Kubota. So my humble advice is to find the Kubota tractor that “looks” like it was loved and buy it without hesitation. You won’t regret it.

    Service Department Vic

  3. Dan Alex Said,

    March 17, 2009 @ 2:31 am

    Hello Geoffrey! I’m all the way from Romania. I bought my Kubota from a dealer of japanese small tractors and I didn’t had the chance to speak to the owner:). So I had to use other tests:
    1. The visual test as Vic said. Mine was not repainted so it shows how much it worked and how it was cared.
    2. The engine test. The engine is the heart of the tractor. I bought mine in january. It had a lot of snow on it and it was – 15 degrees Celsius that day. I started three Kubotas and two other(I don’t want to name them here). Almost all started fine, but this one I liked most. After starting you can check if the smoke is clear. A mecanic I know sais that a clean oil, a smooth run and a clear smoke is the prove that an engine is good. If the smoke is blue, white or black at idle it is not so good. Mine smokes a little blue when cold but it can be fixed in a few years.
    3. The transmision and other. You should test the tractor before you buy it. I made a little mistake and didn’t tested all the features so the PTO is not shifting in gear 1 and 3. But I think it’s a simple adjustment issue. At least I hope.
    Anyway the transmision problems at Kubota are more often at newer models.
    Hope that was useful and more power.

    mine is a L1-R 26 read here about it and my comments


  4. Rick Castiglione Said,

    September 5, 2009 @ 12:37 pm

    Thanks for this terrific website! As a newby to Kubota tractors it is tremendous help!
    Calgary, Alberta

  5. Vic Said,

    September 5, 2009 @ 5:55 pm

    Rick, Glad to have you here! We worked together in the early eighties at CFCN!

  6. tony Said,

    February 11, 2010 @ 9:08 pm

    My L39 is starting to emit white smoke when pushing dirt.It does’nt do it when when I operate backhoe or run at high idle

  7. Peter Said,

    February 17, 2010 @ 11:32 pm

    Glad this site is here, I have an L300DT and I let a couple of people use my tractor, and after wards it no longer wanted to move. I made an adjustment externally to the clutch and it worked. Then I let neighbor borrow it and that was the end of my clutch. I never had such problems when I drove it and I drove it many hours. But, I think the 3 times I loaned it out, they rode my clutch each time.
    I’d like to try the repair myself, since many times you pay someone to do something, you end up having to fix again anyway.
    Is there an adjustment I can make once I open it up , if not, do I need to replace both clutches, since the PTO seems to be working fine? Also, would the Shop Manual be the manual to use to better understand how to attempt this repair myself. I am mechanically inclined.
    Yes, I learned my lesson, don’t loan out something that I need and care about.



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