How does the Kubota BX fuel tank vent?

[Jon Baughman]

I've been to a Blow Mold factory and watched the process of making water tanks. When the plastic is drilled to install something, there is flash (shavings) inside that need removed.

I've read of many problems coming from BX owners who've completely removed the fuel tanks to find shavings and plastic remnants. That's enough validation for me to feel the quality control regarding the issue is nil to none.

I've also seen images of the low quality fuel sending units that are used, covered in rust. Rust draws moisture and creates a breeding ground of more problems.

I am very sure that the fuel tank outlet is not clogged with debris. When I wiggle that fuel pump line off, fuel will just gush out of it.

 

[Jon Baughman]

Update;

Over the late fall and winter, I have continued to experience the same engine shut down.

The symptoms are the same; tractor chokes off and won't start, I can't hear the fuel pump pumping fuel, and when I release the vacuum on the inbound fuel pump line the tractor starts and runs perfectly.

This spring I will post pictures. My son-in-law is a mechanic and has a bore scope for fuel tanks and I will be able to view the inside of the tank to determine if there is debris or not.

I did watch a youtube video where a bx owner removed the fuel tank to clean it out only to discover that it was not dirty. He did discover in the disassembly that the outbound fuel tank line had developed a kink in it from being routed over a pinch point. That kink in his line caused the same symptoms that I am having.

I will try to evaluate that next.

 

[whitetiger]

You have debris in the fuel tank that is blocking the fuel outlet fitting which creates a vacuum in the fuel hose between the pump and the tank. When you remove the hose from the pump suction fitting, it sucks in air which is dislodging the obstruction from blocking the tank outlet fitting. I have seen this scenario several times.

A simple test is to run a piece of fuel hose from the outlet of the secondary filter to the fuel tank fill opening and turn the key switch to the run position to let the fuel lift pump circulate fuel for a while. After a while, the flow will lessen or stop completely which will show that it is obstructed. Also, with the cap off it will rule out the cap vent being obstructed.

 

[GreensvilleJay]

Here's what finally chug,chug, stopped my BX23S It's a tiny, crescent shaped piece of plastic that wedged itself into the 'exit' spigot of the tank. The spigot is maybe 1/4" ID and this was inside it ! Due to the 3 chamber design of the tank and this being black,same material it was impossible to see. ONLY after I removed the tank,blew air in via spigot did water flow out ,so I KNEW 'something' was in the tank. I took a very leisurely 3 days to remove/clean/replace the tank. Help to remove seat and fender pan would have been nice...otherwise an easy job. I've upgraded my 'sink strainer' to a 'cold press mason jar' filter this year.

 

[Vater]

Sorry to resurrect a 2.5 year old thread, but I'm having a very similar issue. I inherited my father-in-law's BX2380 when he passed in April. I remember he asked me last summer to take it to our local repair shop because it wouldn't start. Here are the exact notes from the invoice for what was done:

Unit would not start to drive into shop. Started with changing fuel filters. Noticed a restriction on fuel flow to first filter. Blew air back to tank from there. Fuel flow is good for now but, recommend a tank flush to clean out whatever had it clogged. Removed fuel tank, flushed tank reinstalled, performed the general service and found no other issues with the unit.
ADDITIONAL DESCRIPTION:
HRS 3.50
1. GENERAL SERVICE (BX GEN)
(X) REPLACE ENGINE OIL AND FILTER W/ KUBOTA BRAND FILTER AND OIL CJ-4/SL
(X) LUBERICATE GREASE FITTINGS
(X) RETORQUE WHEEL BOLTS
(X) CHECK BATTERY
(X) REPLACE AIR FILTER
(X) REPLACE FUEL FILTER
(X) ADJUST FAN BELT
(X) ADJUST HST NEUTRAL SPRING
(X) ADJUST BRAKES
(X) CLEAN RADIATOR
(X) CHECK TIRES AND ADJUST PSI
(X) CHECK LIGHTS
(X) CHECK SAFETY SWITCHES
(X) CHECK CONTROLS
(X) CHECK FUNCTIONS
(X) SERVICE MOWER DECK / SHARPEN BLADES
(X) WASH OR AIR CLEAN UNITS IN FIELD
(X) TEST RUN UNIT"

Work was completed on 7/25/25, just under a year ago. I'm almost positive he operated the tractor no more than a couple times for very light work before I took ownership; I did borrow it to plow our driveway over the winter. Since I've owned it, the issue started happening again during the second time I mowed my lawn--revs drop drastically intermittently, and occasionally completely cuts out. It always starts back up, but usually exhibits the same problem. Usually if I let it sit and cool down, it will run normally for 30 minutes to an hour before getting sluggish again. So it's literally been used maybe five times since the shop completely cleaned the fuel system and the issue is back. Loosening/removing fuel filler cap doesn't affect it so I'm fairly certain the cap isn't clogged. I will likely start pulling fuel lines and checking the filters tomorrow to see if there's debris lodged somewhere, but if there's anything else I should look at, I'm all ears. Thanks.

 

[William1]

Sorry to resurrect a 2.5 year old thread, but I'm having a very similar issue. I inherited my father-in-law's BX2380 when he passed in April. I remember he asked me last summer to take it to our local repair shop because it wouldn't start. Here are the exact notes from the invoice for what was done:

Unit would not start to drive into shop. Started with changing fuel filters. Noticed a restriction on fuel flow to first filter. Blew air back to tank from there. Fuel flow is good for now but, recommend a tank flush to clean out whatever had it clogged. Removed fuel tank, flushed tank reinstalled, performed the general service and found no other issues with the unit.
ADDITIONAL DESCRIPTION:
HRS 3.50
1. GENERAL SERVICE (BX GEN)
(X) REPLACE ENGINE OIL AND FILTER W/ KUBOTA BRAND FILTER AND OIL CJ-4/SL
(X) LUBERICATE GREASE FITTINGS
(X) RETORQUE WHEEL BOLTS
(X) CHECK BATTERY
(X) REPLACE AIR FILTER
(X) REPLACE FUEL FILTER
(X) ADJUST FAN BELT
(X) ADJUST HST NEUTRAL SPRING
(X) ADJUST BRAKES
(X) CLEAN RADIATOR
(X) CHECK TIRES AND ADJUST PSI
(X) CHECK LIGHTS
(X) CHECK SAFETY SWITCHES
(X) CHECK CONTROLS
(X) CHECK FUNCTIONS
(X) SERVICE MOWER DECK / SHARPEN BLADES
(X) WASH OR AIR CLEAN UNITS IN FIELD
(X) TEST RUN UNIT"

Work was completed on 7/25/25, just under a year ago. I'm almost positive he operated the tractor no more than a couple times for very light work before I took ownership; I did borrow it to plow our driveway over the winter. Since I've owned it, the issue started happening again during the second time I mowed my lawn--revs drop drastically intermittently, and occasionally completely cuts out. It always starts back up, but usually exhibits the same problem. Usually if I let it sit and cool down, it will run normally for 30 minutes to an hour before getting sluggish again. So it's literally been used maybe five times since the shop completely cleaned the fuel system and the issue is back. Loosening/removing fuel filler cap doesn't affect it so I'm fairly certain the cap isn't clogged. I will likely start pulling fuel lines and checking the filters tomorrow to see if there's debris lodged somewhere, but if there's anything else I should look at, I'm all ears. Thanks.

Probably still has debris in the fuel tank.
I'd...
Check the first filter (PITA) first visually, is it 'white' or 'black' looking. Black typically means fuel contamination. Then I'd....
Pinch fuel line, disconnect from the filter and drain in to a jar. Steady flow? Clean?
Other possibility is the fuel pump itself is failing. A full tank of fuel, gravity should keep you running but below half a tank gets sketchy.
Algae can form if the tractor is left in a humid/wet environment as the tank will 'breathe' and let in moisture, that will then grow algae. Don't ask me how I know this to be true.

A helpful hint from Heloise: When washing your tractor, stick tape over the hole in the tank cap to prevent water ingress. Just be sure to take it off when done washing.

 

[skeets]

William covers a lot of good points ,,now you say you changed the rear filter, just for S&G did you happen to notice how the fuel was coming out of the fuel line it should have been a full hose. If not ,if you have a compressor blow air back through the line back into the tank, lots of gunk can build up and block the out put. If you do that and you get a good flow your tank has a lot of crud in it. Also check the line, they do get soft and will sometimes just collapse not letting fuel through. Now if thats all good head up to the top filter and remove the line and turn it so the lift pump starts if it does then see if it has a good flow. OH and check to see the color of the discharge that there is no water in the fuel. I hope it is all that simple.