Backhoe Backhoe Plumbing on a Kubota L2500

[maule]

I have a Kubota L2500 with a LB400 FEL, I recently purchased a used Bush Hog 760H backhoe. I have called about a half dozen Kubota dealers across the country and none of them see to be able to help me figure out how to plumb the hydraulics. I teed the supply and return for the FEL, but the only time the hoe or the FEL works is when the valves are open on one or the other. One guy suggested a manual diverter valve, and someone else suggested a power beyond connection, but no one seems to know where that is. Bush Hog thinks it may be on the FEL control valve, there are two plugs but I do not know what they are for. Any help would be appreciated.

Thanks, Richard

 

[hayden]

Probably the easiest way to set things up is to plumb the BH in series in front of the loader. This can be done by replacing the connection between the supply line and the loader valve with a quick-connect coupler. When the BH is removed, the supply line connects directly to the loader valve. On the BH lines, which will need to run all the way up to the loader valve, you put the two halves of another quick-connect on each of the lines. When the BH is installed, you disconnect the supply line from the loader valve, and couple it to the supply line of the BH, and the BH return line couples to the loader valve. Fluid now flows through the BH, then through the loader. This will work fine, and is how Bradco recommends their hoes be connected. You will need to be careful to get the male/female coupler ends put in correctly so the loader supply line mates to the BH supply line, and the BH return mates to the loader connection.

 

[hayden]

Here's more detail per my private email in case there are others who want to do this.

Do you plan to permanently install the BH or will it be removed/replaced? If it will be a permanent installation, then you could hard plumb it without quick disconnects. If you want to be able to remove it easily, then use the quick connects.

I'd suggest tapping the PB line. That's the fluid leaving the loader valve and going to the 3PH or other implements, and is the third hose on the top of the loader valve. This carries any pressurized fluid not used by the loader to "power" implements "beyond" the loader, hence the term Power Beyond. If the loader is fully activated, all fluid coming in the IN port flows to the loader cylinders and nothing flows through the PB port. The other extreme is no loader activity in which case all the fluid coming in the IN port flows to the PB port. For reference, the OUT line goes straight to the tank carrying any fluid expelled from the loader cylinders as you move them in one direction or the other. The IN line is fluid coming from the pump.

You could tap in as follows. You'll have to figure out exactly what fittings and adapters will be needed to make everything connect up. Tap the PB line, not the IN line. The IN line will work, but it will not be protected by the pressure relief valve in the loader valve. Tapping the PB line will give an extra measure of safety.

1) Remove the PB line where it connect to the loader valve

2) Install a female quick connect body on the PB port of the loader valve

3) Install a male quick connect nipple on the PB hose.

Note: Coupling these two together restores you hydraulic system just as it was before.

4) Put a female quick connect body on the IN line going to the BH

5) Put a male quick connect nipple on the OUT line coming from the BH

Now if you disconnect the tractor line from the loader valve, and connect the tractor line (male) to the BH IN line (female), and the BH OUT line (male) to the loader PB port (female), you should have a functioning loader and BH. Beware that the BH will always be powered, so bumping the controls will send it moving. To deactivate it, just disconnect the lines and hook them back up to the loader.

Oh, one BIG BIG BIG NOTE: This connecting and disconnecting of the lines can ONLY be done with the tractor shut off and hydraulic pressure relieved. In an "Open Center" hydraulic system like you have, fluid is ALWAYS flowing. If you disconnect the line to the loader, you will be blocking the system and forcing everything through the loader relief valve. Not a good idea.