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  1. #1
    Bronze Member
    Join Date
    Dec 2009
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    95

    Default How to adjust main relief psi setting on B21

    Hello everyone - I would like to set my main hydraulic relief a little bit higher on my B21, specifically for my loader lift capacity. I noticed on my loader control valve, there is no main relief valve to control the max pressure. I am very familiar with the valve since I work for the company that makes them

    Does anyone know where on the machine the main pressure setting is controlled and how to adjust.

    Please note that I do not intend to go crazy, I just want a little more. The unit is designed to lift 1000 lbs - my feeling is that it is limited due to counter weight. The loader arms look strong enough to me to lift a little over 500lbs each.

    Thanks
    Scott

  2. #2
    Super Member
    Join Date
    Apr 2000
    Posts
    5,662
    Location
    Cedartown, Ga and N. Ga mountains
    Tractor
    1998 Kubota B21, 2005 Kubota L39

    Default Re: How to adjust main relief psi setting on B21

    Scott the relief valve is set by shims under a spring in the valve system. You can buy them from kubota. I would sure recommend that you put a pressure gauge on the system to see what you have before you up it. I can't recall what the setting is suppose to be but I think it is 2100 psi. A shop manual would tell you. Might also want to want to do a search on the forum. Several have done it on other tractors.

    MarkV

  3. #3
    Platinum Member
    Join Date
    Sep 2008
    Posts
    841
    Location
    Central, AR

    Default Re: How to adjust main relief psi setting on B21

    The parts manual lists 4 relief valves. 3 are on the HST and one called the body relief valve. The body relief valve is part of the hydraullic outlet that may attach to the oil tank.

  4. #4
    Silver Member
    Join Date
    Jul 2010
    Posts
    144
    Location
    Huntsville AL
    Tractor
    BX200D w/FEL, B21 TLB, KX91-3SS. F700 Dump Truck

    Default Re: How to adjust main relief psi setting on B21

    Quote Originally Posted by BruceWard View Post
    The parts manual lists 4 relief valves. 3 are on the HST and one called the body relief valve. The body relief valve is part of the hydraullic outlet that may attach to the oil tank.
    Bruce, where did you see these valves? I found 1 main pressure relief valve on the hyd block on top of the HST, and several what I believe are check valves which prevent damage, they are labeled poppet C.V in my parts manual. The shop manual also calls out several check valves on the loader itself. I did find an overload relief valve on the backhoe though, so this may need to be tweaked as well if the main pressure is increased, its opening range is 2420 - 2490

    The pressure release valve on the B21 has a screw adjustment- at least mine does. The pressure range is 1991 to 2062 psi, according to the shop manual. There is a plug next to the valve to connect a gauge. The manual also calls out a procedure for checking the pressure at the loader control value, basically just disconnect the bucket curl hose and put the gauge there, it should be the same.

    I've been meaning to check my pressure, but have not got around to it yet. Mine can pick up logs heavy enough to make the back end feel light with the backhoe attached, but I'd like a little more ripping force on the backhoe to tear thru roots.

    Tony
    Last edited by TonyF; 09-05-2010 at 10:02 PM.

  5. #5
    Platinum Member
    Join Date
    Sep 2008
    Posts
    841
    Location
    Central, AR

    Default Re: How to adjust main relief psi setting on B21

    I looked at a B21 parts catalog that I found by searching Google.

    If you look at this PDF http://www.jwnet.net/Documents/Kubot...20List/B21.pdf and search for the word relief you can find relief valves listed on page 149 and 262.

    I did not find a relief valve listed in the FEL parts catalog.

    I see the backhoe relief valve listed on page 36 of this PDF http://www.jwnet.net/Documents/Kubot...List/BT751.pdf

    Tony, if you do adjust your relief valve I would love to see pictures and any writeup you put together. I have occasionally thought about testing or adjusting the FEL pressure but I have almost no experience with hydraulics.

  6. #6
    Elite Member dfkrug's Avatar
    Join Date
    Feb 2004
    Posts
    4,444
    Location
    NorCal
    Tractor
    05 Kioti CK30HST w/ Prairie Dog backhoe

    Default Re: How to adjust main relief psi setting on B21

    Here is the system relief valve, from the parts book, #20 in the drawing.
    It is on the lower right hand side of the rear of the tractor, below your
    diverter lever. I can post a photo if you need one.
    Attached Thumbnails Attached Thumbnails -relief_valve-jpg  
    See my TBN projects at:
    http://mysite.verizon.net/resyfcgt/

  7. #7
    Silver Member
    Join Date
    Jul 2010
    Posts
    144
    Location
    Huntsville AL
    Tractor
    BX200D w/FEL, B21 TLB, KX91-3SS. F700 Dump Truck

    Default Re: How to adjust main relief psi setting on B21

    Quote Originally Posted by BruceWard View Post
    I looked at a B21 parts catalog that I found by searching Google.

    If you look at this PDF http://www.jwnet.net/Documents/Kubot...20List/B21.pdf and search for the word relief you can find relief valves listed on page 149 and 262.

    I did not find a relief valve listed in the FEL parts catalog.

    I see the backhoe relief valve listed on page 36 of this PDF http://www.jwnet.net/Documents/Kubot...List/BT751.pdf

    Tony, if you do adjust your relief valve I would love to see pictures and any writeup you put together. I have occasionally thought about testing or adjusting the FEL pressure but I have almost no experience with hydraulics.
    Bruce, I understand now. Some of the relief valves shown in those diagrams are for the hydrostatic transmission, which is separate from the hydraulic system. The two systems, hst and hydraulic share the same oil and reservoir, but that's about it. I would recommend against messing with the hst.

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