B2710 Hydraulic Relief Valve adjustment

[GhostRider29]

Hello Kubota folks,
I have a few question. I am trying to adjust the psi on my B2710 HST, as the FEL and 3PH felt weak. Before I start with the questions, I want to give a little background. I replaced all rubber hoses, o-rings (that I could locate on the workshop manual), hydraulic fluid strainer, hydraulic fluid and filters. The B2710 has a Bush Hog FEL on it there are no quick connectors between the control stick and FEL, just the two hoses one is outlet and other one inlet. I unplugged the quick connector between the outlet port and control stick and plugged in the pressure tester on the end from the outlet port. The relief valve setting pressure (factory spec.) should be 1920-1991 psi. I got a hydraulic pressure tester from Amazon for Kubota B, BX, L… series. The original shim was kinda worn out. There was only one washer and one 0.2 mm shim. The psi reading was around 1,200 psi. I replaced it with a set of two new washers (as suggested from the workshop manual) and one new 0.2 mm shim. The pressure went up to around 1,550 psi. I took out the new 0.2 mm shim and replaced it with one 0.4 mm. The psi when up to around 1,800 then dropped to 1,200 suddenly psi. I have no idea why it did that. Before I changed from 0.2 mm to 0.4 mm shim, the 3PH with ballast box would lift at low rpm with no problem. Now it won’t with the thicker shim. I read somewhere that it is normal. I tested the FEL after taking out 0.2 mm and putting in 0.4 mm and it’s a lot stronger but I wonder why the tester shows low psi reading. Is there something wrong or is it normal? Lastly, is there a better way to connect the tester other than the outlet port?

 

[North Idaho Wolfman]

First off your using the wrong term in your thread title.
As the HST Relief valve has NOTHING to do with hydraulic system pressure, they are different systems.
I'll change the title.

You are getting erroneous readings because you're measuring it wrong.
You can't disconnect a power supply loop and put a gauge on it like that.
You need to put the gauge on an output to the loader cylinder.

Also, I'm betting since you have an aftermarket loader on it, that that loader valve will also have a relief valve on it.
You'll need to set both reliefs to get it to work properly.

 

[GhostRider29]

First off your using the wrong term in your thread title.
As the HST Relief valve has NOTHING to do with hydraulic system pressure, they are different systems.
I'll change the title.

You are getting erroneous readings because you're measuring it wrong.
You can't disconnect a power supply loop and put a gauge on it like that.
You need to put the gauge on an output to the loader cylinder.

Also, I'm betting since you have an aftermarket loader on it, that that loader valve will also have a relief valve on it.
You'll need to set both reliefs to get it to work properly.

Thanks for your response and editing the title. I was going to edit the title as it’s just a habit to add HST because when I do search online on B2710 the term HST tends to come up after B2710. I don’t mean the relief valve on the HST.
Yeah I thought about connecting the tester to the output hose that goes to the loader cylinder. Will I still have erroneous reading because the other cylinder (other side) will operate at the same time?
For the loader relief valve, I am sure it’s located somewhere on the valve (control stick) housing? Should I put the 0.2 mm shim back in and take out the 0.4 mm shim?

 

[TheOldHokie]

First off your using the wrong term in your thread title.
As the HST Relief valve has NOTHING to do with hydraulic system pressure, they are different systems.
I'll change the title.

You are getting erroneous readings because you're measuring it wrong.
You can't disconnect a power supply loop and put a gauge on it like that.
You need to put the gauge on an output to the loader cylinder.

Also, I'm betting since you have an aftermarket loader on it, that that loader valve will also have a relief valve on it.
You'll need to set both reliefs to get it to work properly.

No - as long as the main system relief is in the circuit his test is 100% correct. It also eliminates the loader relief from the circuit ensuring he is measuring the main system settimg and not the loader setting. I will also note that if his loader valve only has two hoses going to the tractor the loader reIief will not effect the 3pt pressure.

Dan

 

[TheOldHokie]

Thanks for your response and editing the title. I was going to edit the title as it’s just a habit to add HST because when I do search online on B2710 the term HST tends to come up after B2710. I don’t mean the relief valve on the HST.
Yeah I thought about connecting the tester to the output hose that goes to the loader cylinder. Will I still have erroneous reading because the other cylinder (other side) will operate at the same time?
For the loader relief valve, I am sure it’s located somewhere on the valve (control stick) housing? Should I put the 0.2 mm shim back in and take out the 0.4 mm shim?

See my response above.

I looked at the parts diagram for B2710 and the main system relief is in the 3pt cover which is after the loader valve. The outlet block for the loader valve is directly after the pump and us not protected by a relief.

Exactly where are you cinnecting your gauge?. My initial thought was you connected it to the return hose on the liader valve. If that were the case there would be no relief in the circuit and you would be deadheading the pump and at odds wirh your results!!!!

Dan

 

[PoTreeBoy]

See my response above.

I looked at the parts diagram for B2710 and the main system relief is in the 3pt cover which is after the loader valve. The outlet block for the loader valve is directly after the pump and us not protected by a relief.

Exactly where are you cinnecting your gauge?. My initial thought was you connected it to the return hose on the liader valve. If that were the case there would be no relief in the circuit and you would be deadheading the pump and at odds wirh your results!!!!

Dan

According to the schematic in the WSM, this tractor has front and rear hydraulic blocks. The front one is before the tractor relief, and the rear one (located on the 3pt hitch, I think) is after the relief.

I think some pictures of his valve and the tractor connections would be helpful.

 

[TheOldHokie]

According to the schematic in the WSM, this tractor has front and rear hydraulic blocks. The front one is before the tractor relief, and the rear one (located on the 3pt hitch, I think) is after the relief.

I think some pictures of his valve and the tractor connections would be helpful.

More than helpful - necessary.

The LA401 uses the front block and has pressure, power beyond, and tank return connections to the tractor.

Dsn

 

[PoTreeBoy]

More than helpful - necessary.

The LA401 uses the front block and has pressure, power beyond, and tank return connections to the tractor.

Dsn

He has a Bush Hog loader, so ???

 

[TheOldHokie]

He has a Bush Hog loader, so ???

My pount was he said the Bushog only had two connections - e.g no power beyond. If thats the case connecting a gauge to the "outlet" hose deadheads the pump. He would be reading umrelieved pump outlet pressure which should be much higher than amything he reported.

Something (lots of things) wrong in his description.

Dan

 

[North Idaho Wolfman]

My pount was he said the Bushog only had two connections - e.g no power beyond. If thats the case connecting a gauge to the "outlet" hose deadheads the pump. He would be reading umrelieved pump outlet pressure which should be much higher than amything he reported.

Something (lots of things) wrong in his description.

Dan

I had a b7100 with only 2 hoses and it was hooked up before the rear relief valve.
Yes it was hooked up wrong, but that was the way it worked for years.

 

[TheOldHokie]

I had a b7100 with only 2 hoses and it was hooked up before the rear relief valve.
Yes it was hooked up wrong, but that was the way it worked for years.

I didnt say it would not work. What I did say is with that plumbing the loader relief if present has no effect on 3pt pressure.

Dan

 

[GhostRider29]

I bought this tractor used several years ago and that is the way it was. It has been working great but not as strong as it should be. It’s hooked to the front block. I’ll test it on the loader itself. Here are some pictures to help visualize. At first I connected the gauge to the quick connector from the outlet part of the block and now I know it’s not the correct way to do it. should I change back to 0.2 mm shim as it will not make any change to the FEL itself except 3PH.

 

[TheOldHokie]

I bought this tractor used several years ago and that is the way it was. It has been working great but not as strong as it should be. It’s hooked to the front block. I’ll test it on the loader itself. Here are some pictures to help visualize

I see three quick connects. That suggests the valve has three connections to the tractor.

The loader vslve is ahead of the tractors PRV and testing at the loader valve will tell you nothing about the setting of the tractor's PRV (3PT). It will tell you what the loader relief is set at and if thst is lower than the tractors PRV (3pt) will overide the tractor setting.

Dan

 

[GhostRider29]

I see three quick connects. That suggests the valve has three connections to the tractor.

The loader vslve is ahead of the tractors PRV and testing at the loader valve will tell you nothing about the setting of the tractor's PRV (3PT). It will tell you what the loader relief is set at and if thst is lower than the tractors PRV (3pt) will overide the tractor setting.

Dan

The third one will go to the return port (transmission case).

 

[TheOldHokie]

The third one will go to the return port (transmission case).

Yes, and that means the loader relief is in the circuit AHEAD of the tractor relief.

To test and adjust the tractor relief you must first make sure the loader relief is set to a higher cracking pressure. If the loadet valve is set lower you can never get the tractor relief to open.

To test and adjust the tractor relief you must connect the gauge to the test port under the seat as shown in the wotkshop manual. Alternatively you can put a tee in the loader pressure in or power beyond line and use that as a test point. That would be my choice.

Dan

 

[GhostRider29]

Yes, and that means the loader relief is in the circuitc AHEAD of the tractor relief.

To test and adjust the tractor relief you must first make sure the loader rekief is set to a higher cracking pressure. If the loadet vslve is set lower you can never get the tractor relief to open.

To test and adjust the tractor relief you must connect the gauge to the test port under the seat as shown in the wotkshop manual. Alternatively you can put a tee in the liader pressure in or power beyond line and use that as a test point. That would be my choice.

Dan

Thank you. That’s very helpful. I really appreciate it.

 

[PoTreeBoy]

The third one will go to the return port (transmission case).

OK. There is a relief valve in the loader valve and one in the 3pt housing. Which one have you been shimming? If you've been shimming the 3pt one, you're not going to affect the loader 'strength'. I'd put it back the way it was, if the 3pt lifts to your satisfaction.

As The Old Hokie says, the front relief controls the pressure that the loader sees. The lower of the two determines the pressure that the 3pt sees.

 

[GhostRider29]

OK. There is a relief valve in the loader valve and one in the 3pt housing. Which one have you been shimming? If you've been shimming the 3pt one, you're not going to affect the loader 'strength'. I'd put it back the way it was, if the 3pt lifts to your satisfaction.

As The Old Hokie says, the front relief controls the pressure that the loader sees. The lower of the two determines the pressure that the 3pt sees.

Yes, I just put the ori shim back in. I found the relief valve on the loader valve housing. i just downloaded the Bush Hog FEL manual explaining how to adjust the relief valve.