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Thumb problems KX-71

Discussion in 'Compact Excavators' started by Someotherguy, Aug 27, 2012.

  1. jack345

    jack345 Well-Known Member

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    Great thread on the Kubota Kx model no relief valve problem. I have a Kx61-2 that when I purchased it had bent bucket pin due to PO using both bucket and thumb hydraulics at same time. I use mine as a manual thumb hoping to get info on how to adjust-since that won't happen anyone fixed there Kx yet ? Pics? Thanks
     
  2. TCM

    TCM Well-Known Member

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    Here is a pic of what I had to do to relieve my Aux line. Should have done it a long lime ago. It's pressure adjustable for the times I use other attachments (ie wood splitter). The return line frome the valve goes to the return manifold onder the seat (capped from factory). It steps down to .25" is the only problem I can see, however it does work. Thanks for the advice (you know who you are).
     

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  3. willie59

    willie59 Super Moderator

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    Very nice work TCM. :cool:

    And the way you have it configured, wouldn't be hard at all to add an additional relief on the other line. ;)
     
  4. jack345

    jack345 Well-Known Member

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    Thanks for pic, I have the same Aux line Configuration on my Kx, Having the valve one line is its operated to where you set the thumb in place and then the bucket will over power the thumb? Thanks.
     
  5. TCM

    TCM Well-Known Member

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    Yes it will. In addition I have the quick couplers opposite each other so you can't mix the lines up. That is a single relief valve only relieving one side of the aux circuit.
     
  6. Justin Payne

    Justin Payne Active Member

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    Hello Willie59, please have a look at my valveblock of my Kubota U50-3@ 2006 model:
    Valve block.JPG
    I am about to install a hydraulic thumb and need to make sure I will not ruin it straight away. Most of my circuits/spools here have 2 relief valves (one on each side of the valveblock) and I don`t see any other "in line" valves (I can follow the lines from the spools to the hydraulic cylinders without finding any extra valves). When reading your explanation above it sounds like these relief valves will not fully protect the bucket/stick/ blade etc. if they are inflicted forces upon while not in use.. Is this correct? I want to connect a thumb to my aux spool and hope that i only need to mount in relief valves just as the bucket/stick and blade already have in their spool. I am hoping these valves dump the oil to their "twin line" from the same spool + tank (if it is coming from extension side of piston)...
    Would be very grateful for any explanations :)
     
  7. willie59

    willie59 Super Moderator

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    Hi Justin, I can't say for certain because I'm not familiar with your machine, but those reliefs you have marked look like port reliefs for the noted functions. If they are port reliefs, they will pop open and relieve the cylinder/function noted even when the spool is centered. Not sure about your aux section, I see something that looks adjustable in that port, just can't tell if it's a port relief or not. If you could get your hands on the hydraulic diagram for your machine you could get more info from that, might even get some useful info from the parts pages, I think you can look up Kubota parts pages online.
     
  8. jack345

    jack345 Well-Known Member

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    1024_HPIM1643.JPG 1024_HPIM1642.JPG Justin, on my Kx there was NOT a relief on the aux port. As stated above it will cause problems. Corrected problem by installing a adjustable inline relief valve. See pic
     
  9. jack345

    jack345 Well-Known Member

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    Before & after install pic
     
  10. lantraxco

    lantraxco Senior Member

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    Ummm.... Jack? Read back on this thread, Willie's explanation about how the exact valve you're using is dangerous in a two way cylinder application. I've lost the pictures, but I proved it to my then boss thirty years ago when a valve that looked very much like the one you have there literally blew in half the length of the casting. This was after upgrading hoses several times because they kept blowing ends off and such before I was employed there. You have to have a tank line to handle the relief flow, you can't just move oil from one end to the other.
     
  11. Justin Payne

    Justin Payne Active Member

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    Thanks Willie59, Jack and Lantraxco for you comments! Could you have a look at the attached the parts diagrams for my aux and bucket spool?
    And tell me if you think these relief valves on the bucket spool are port reliefs? (They are described as "Assy relief valve" in the parts list..) The corresponding parts in the aux parts list are described as "Assy valve shut of"..They do not look as if they contain any spring, so I can`t believe they have any valve function.
     

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  12. Justin Payne

    Justin Payne Active Member

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    Here is my aux spool diagram/parts list: :)
     

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  13. willie59

    willie59 Super Moderator

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    Yes, the diagram for the bucket spool section shows port reliefs, item(s) 180. The diagram for the aux spool section with the assy valve shut off, that's not a port relief valve, but it is installed in a port relief port. To try to explain it as simply as I can, the way those type of valves work is when the spool is in the center position the work ports, typically called A and B, are blocked from both oil input from the pump (P) and oil output to the tank (T) by the spool itself. In other words, the oil in lines connected to A and B, lines that go to cylinders/motors, is effectively trapped in in those lines by the spool in the centered position. If the attachment that is connected to ports A and B encounter an external force, putting external force pressure on either A or B, at some point something has to give. That's where the port relief comes in, it's an internal (inside the valve) route for oil under pressure in A or B to escape and exit to tank (T), by-passing the spool.

    In the case with your aux section with the "assy valve shut off", basically that's plug that plugs that internal route between A and B and the internal tank porting, it blocks off that route. If it were not there, when you worked a function connected to A or B on the auxiliary section oil would simply go right through the valve to the tank porting, no work could be performed with A and B lines, so they plugged that internal port. That also means you have no port relief on the A and B of the aux section because of this plug. However, it's very possible that the relief valve cartridges that are used in the other sections, such as the bucket section, will fit in the port relief ports on the aux section. Remove the "plugs" and install relief cartridges. I can't say for sure this will work because I don't know that machine, but a Kubota parts guy should be able to confirm this.
     
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  14. Justin Payne

    Justin Payne Active Member

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    Hello Willie, Thank you very much for your splendid explanation. That is what I also wanted to hear, so now I will just need to buy a couple of these port reliefs and install them straight in the aux spool :)
     
  15. willie59

    willie59 Super Moderator

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    That's what it looks like, but again, I'd confirm with Kubota
     
  16. Justin Payne

    Justin Payne Active Member

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    After some searching on the internet I find that these original relief valves are really heavily priced... $330 each !
    I found a stock with just the one for half the price which I have ordered. And now I am wondering if I can manage with just the one..? Does anybody have a opinion whether it is just as important to have one on the "extension side" of the thumb cylinder?? I am wondering if I could manage without a pressure relief valve on that line, and rather be careful not to put external force on the back side of the thumb.. Or will the fully retracting the cylinder then cause damage?
     
  17. willie59

    willie59 Super Moderator

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    If that's 330 US Dollars, actually that's not bad, I've paid over $800 for Kobelco port relief valves. But hey, sometimes the wallet gets thin, I know that feeling. In a pinch, if you're the only one operating the machine, yes, you could get by with only one relief valve on the extend side of the cylinder. No, it's not the ideal set up, but do-able if you keep your wits about you when retracting the thumb.