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Thread: Problem with a Kobelco SK300LC mark IV

  1. #1
    Junior Member
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    May 2011
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    california
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    Problem with a Kobelco SK300LC mark IV

    Hello I am new to this forum and was very excited to find it, I have been a heavy equipment mechanic for many years, I have a Kobelco SK300LC mark IV sn:ycu0756. I installed a thumb and two-way auxiliary valve, and finding info on this mark IV is not easy, I bought the factory service Manuel and serviceman's hand book however they don't seam very complete, I haven't found a schematic so I can electrically stroke the pump so that I can have pressure to run the thumb, it moves now very slow because it only has 250 LBS of hyd pressure. on the foot control there is a elect pressure switch with two wires to the harness but they have no power and don't seam to affect anything. we bought the excavator a while back at the auction and it looks like it at some point had a thumb and valve and someone took it off before they sold it not sure?. I understand that when the mark IV machines came out Kobelco went out of business and was taken over later and came out with the -6's? not to sure about that however i was told that there was not much info out there for mark IV.the main control valve is made by Kawasaki and on each side there is ports for the right and left pump pressure and smaller ports to activate them however I still need to stroke the swash plate in the pumps to have press. If I had a detailed schematic I could figure out witch wire to connect to. has any one run across this problem with the Kobelco mark IV before, I have talked to two Kobelco dealers and both said that because of the lack of info they would never have taken the job on but I work for a demolition company and this is one of there excavators so I have to fix it.I can post some pictures if I need to any info would be appreciated.

    Thanks Tim

  2. #2
    Senior Member
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    Mar 2011
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    allendale mi
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    165
    You can not stroke your pumps electrically, dont try you will burn your cumputer, which pump did you tap into for main pressure for aux? Did you use a pilot oil cntrolled aux valve or electric? You are going to have to stroke your neutral cut valve in your main controll valve to move oil to your aux but you have to know which pump you taped into. Stroking the pumps only builds flow, it is the resistance to that flow that is pressure. those pumps will hold 4000 psi if you have the thing hooked up corectly. I can tell you where that spool is but I don't have a manual in front of me right now, i'll pick one up next time I get to the shop. Somebody should open a kobelco dealership in CA, there's lots of info avalible for the mark 4's.

  3. #3
    Junior Member
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    May 2011
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    california
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    grandkobelco, I was told by the Kobelco dealer by me that there was not much info for mark IV's? here is what i have done, I took a two-way auxiliary valve from another machine and a joystick control and two electric over hyd valves, so far i tapped into each end of the factory control valve for auxiliary fluid because they were plumbed previously like i said someone had a auxiliary valve on here before, I used pilot pressure to activate them right and left sides, the left has a shut off valve on the pilot and pressure so i can use it when i need more flow, the auxiliary valve takes at least 1000 psi to move the spool, so one valve is for the pilot pressure to the control valve and the other is to move the auxiliary valve both are controlled by one joy stick switch momentary on-off-on with diodes in-line, I work for a rather small company that like everyone else is struggling, so I have to work with what I have, i hope you understand i wish things were different but, so when i put pilot pressure to the main control valve i only have 200 to 250 lbs i was told that i have low pressure because i need to stroke the pump electrically to build pressure?, now if i don't have the valve open and supply pressure it will kill the engine as it should. the thumb opens and closes slowly in each direction.

  4. #4
    Junior Member
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    May 2011
    Location
    california
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    9

    problem with a Kobelco SK300LC mark IV

    If this helps this is where my main control valve is tapped into for the pressure for aux and pilot cntrolled aux.

    [IMG]http://i1121.photobucket.com/albums/...909/kob002.jpg[/IMG]

    [IMG]http://i1121.photobucket.com/albums/...909/kob001.jpg[/IMG]
    Last edited by beckco909; 05-26-2011 at 04:49 PM.

  5. #5
    Resigned
    Join Date
    Jul 2008
    Location
    CANADA
    Posts
    433
    hi, the pilot oil will need to run thru your elec/hyd 3-way dcv. and will need to signal ports " pop1 " and " pop2 "
    in order to stroke up the hyd pumps by shifting the neutral cut spools.
    when not energised, the pop ports will need to drain off to tank to release the pumps returning back to neutral.
    ports pop are a 1/4" jis bspp thread.
    however, for a hyd thumb you should only require flow from one pump.
    too much gpm and pressure you will risk bending the rod of the hyd thumb like a banana.
    as far as rising the engine rpm you will need to install a pressure switch GB50S00049F1
    the pilot oil via shuttle will energize the pressure switch and ground the decel wire to tell the computer to go full engine rpm.
    if you e-mail me at hf_hydraulics@hotmail.com
    i can send you more info on the nibbler/breaker setups.
    very helpful for you.
    cheers!

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