Backhoe Kubota B20 with BT750 backhoe: Auto Return feature

[dfkrug]

Recently got another tractor project, a 30 year old Kubota B20 TLB. Neglected, and needing lots of minor repairs.

Question: has anyone who has owned, used, and/or worked the integrated backhoe, BT650 or BT750 know much about the Auto Return feature? It seems Kubota gave up on this function when they stopped making the B20. The replacement B21 did not have this feature on its hoe, the BT751.

Anyway, this function swings the boom automatically, and utilized 2 solenoid valves and an electronic controller. Not easy to bypass, apparently. I can't test my hoe yet, as I need to rebuild 2 cyls first, plus change 6 hoses.

 

[goeduck]

I have a B21 and like you say, no auto return. Let us know how the hoe hose replacement goes, I need to do mine. I did the FEL. Will you be buying the hoses retail or having them made up?

 

[Carl_NH]

DFKrug,

Good too see you have another project the Kubota I followed your last rebuild on the B21. There are a few threads here you might want to review.. https://www.tractorbynet.com/forums/kubota-owning-operating/4738-bt-750-auto-return.html

Looks like you will need get into that valve stack which can get $$ unless you find a donor!

Post some pics of your project.

 

[dfkrug]

There are a few threads here you might want to review...

Yeah, I found only 3 threads earlier this week referring to the BT650/BT750 Auto Return in my initial TBN search. I was hoping some active members who have or had the B20 would give their feedback.

I am now in wait mode for parts (Messicks). Kubota's prices on the hoses and seal kits are quite reasonable actually. That is not always true. The six hoses that go inside the boom range from $27 to $59 each. The seal kits range $21 to $24 each. Hercules would be somewhat less for the seals, but it is not worth my time going that route. Besides, getting the full kit will make it so I replace ALL the seals, not just the bad ones.

Note that the BT hoes are very well-made. The boom cylinder is huge: 3.5" OD, and 35mm rod. BUT...you have to remove it from inside the boom to access the 6 hoses. BTW the gland-to-rod seal on this cyl was blown out in pieces. All the cyls are different sizes.

The changes from the B20 to the B21 were huge. I will post some pix.

 

[dfkrug]

OK, here are some pix.

The trailer this unit came in on is amazing. The whole deck lowers pneumatically and stays level. No ramps needed. It self-levels automatically as well.

Anyway, 2 pix of under the hoe control panel. The controller is one the left, and the large proportional solenoid valves are on the right-most section of the valve stack. In the last photo, you can see the 2 LEDs on top of the controller. One is red, and one, green. Power is going to the unit, but there is no pressure since the engine is off. I hope that is why one LED is red.

 

[dfkrug]

Well, I spoke too quickly. Messicks lists the parts I need (hoses and seal kits), but cannot get some of them. :-(

So I will have to get the seals for the big cylinder (70mm bore, 35mm rod) from somewhere else. The hoses are not problem, as they are 3/8", with JIC -8 ends. Even Hercules does not have the piston seal (66x70x3), so I will either not replace it, or cut the groove wider to fit a wider seal.

The big cylinder has an aluminum gland, and I had to resort to my biggest wrench to get it off. I was almost to the point of trying heat, but the 36" pipe wrench with 2" pipe extender did the trick.

 

[dfkrug]

The gland seals are a mess, but the others are OK.

I think this is the first cyl I have rebuilt that uses a bolt, rather than a nut, to hold the piston on. Some BT750s install the boom cylinder with rod up, and some install it reversed, according to the parts book.

The oil has a lot of water in it, but I do not see how so much gets in. It does sleep outside, and sometimes gets rained-on.

 

[goeduck]

Some not so good looking fluid in there. But nice job getting that apart :thumbsup:

 

[dfkrug]

Some not so good looking fluid in there.

Yeah, some nasty-looking vanilla milkshake. Thanks. So far, got about 5-6 gallons out. I try to articulate the FEL and hoe with my Kioti to squeeze out as much as possible before I replace it. My plan is to use Soundguy's Elixer (diesel + ATF + isopropyl alcohol) to flush.

That is how I ran into issues with the Auto Return function. You cannot swing the hoe boom without energizing the swing solenoids. And I do not want to start the tractor without oil in the sump.

Note that the B20 has 2 hydraulic filters, and I will flush and drain first, replace the filters, then add THF. There will still be some water in there, but a lot less.

 

[Industrial Toys]

That was a most interesting trailer. Who knew?

You could try Canada for parts. Recently spoke with Messicks about a rad for my R510 and none was availabla in the states but Canada has some. Weird, I know. USA does not have access to that inventory information.