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Thread: Kubota motor help

  1. #1
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    Kubota motor help

    Hi all.
    A mate has asked me to help him out with his Bobcat excavator motor.
    The excavator fell over onto it side while running a while ago, not sure how the motor was stopped or if it stalled.
    It is a 3cyl kubota motor. After it was pulled upright (a few days later) the glow plugs were pulled and was turned over, apparently a little bit of crud was blown out.
    It does run, but blows a lot of white smoke and sounds like it is down on power on a cyl. When the injectors are cracked the smoke stops on #2cyl. the injectors were sent away and rebuilt but no difference.
    A strange bit is every once in a while the smoke stops and it runs fine for a short time, and then goes back to running like ****.
    I have my theories about what is wrong but would like to hear anyones else ideas before i pull it apart. I dont have a compression tester and it is 6hrs away so I cant do any quick checks.
    Any thoughts?

  2. #2
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    Can't be of too much help. My guess is either damaged rings or carbon residue from oil seeping past rings while on side.

    I have a Kubota 3 cylinder tractor and stalling it in normal circumstances should not cause a problem. On its side, maybe fuel starvation if the tank is gravity feed to injector...oil starvation to the crank and sieze...sump oil filling the underside of the cylinder making piston cycling difficult, eventually stopping the engine.

    Crud I would think is sump oil having leaked past the rings.

    Did you use CRC or such to get it started again? Or did it start of its own accord on the starter? Ether shouldn't be used on diesel engines unless manufacturer specifies its use - otherwise you risk damaging the rings from premature ignition (my understanding).

  3. #3
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    probably stalled out, Im going to go with fouled ring, bent rod or a valve with a contaminated seat. thats not closing properly.

    check the blowby while you crack the offending injector if the blowby backs off or the beat doesnt change much its going to be one of those 3. if it sorts itself out when it warms up or you work it hard its the rings stuck.
    Dave

    "In a Landrover the other vehicle is your crumple zone."

    For spelling call Rogets, for mechanicing call me.

    Fozzy, 2.25D SIII Ex DCA Ute
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    Archaeoptersix 1990 6x6 dual cab(This things staying)


    If you've benefited from one or more of my posts please remember, your taxes paid for my skill sets, I'm just trying to make sure you get your monies worth.
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  4. #4
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    I'm was for cracked or fouled rings as my guess.
    Started easy of its own accord, is the same warm or cold, I don't know about working hard yet. I will check for blow by before I start. Hadn't thought about valve seat, I should be able to check valve clearance for that. Anyway I go the head has to come off I imagine. The way it has spurts of good running occasionally gave me thoughts of cracked rings lining up every so often.
    I have a week before I get down there, I will see if we can hire a comp tester to rule rings in or out.

  5. #5
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    Quote Originally Posted by Albert View Post
    I'm was for cracked or fouled rings as my guess.
    Started easy of its own accord, is the same warm or cold, I don't know about working hard yet. I will check for blow by before I start. Hadn't thought about valve seat, I should be able to check valve clearance for that. Anyway I go the head has to come off I imagine. The way it has spurts of good running occasionally gave me thoughts of cracked rings lining up every so often.
    I have a week before I get down there, I will see if we can hire a comp tester to rule rings in or out.
    you dont need a compression tester to rule things in or out.

    whip the injectors or glow plugs out (if you have glow plugs do it this way its easier) and put compressed air onto the hole while you work the engine over by hand and listen to the inlet, the exhaust and with the dipstick removed and the crank case breather blocked listen at the dipstick hole.

    if it has moments of good running it could be the valve as it rotates or its rings.

    if its the rings your first step is a lightly loaded high speed run of the engine with an oil with a good detergent package or add some DEX III shock loading the thing may also help free up the rings.

    while the plugs or injectors are out use a small screwdriver to check the TDC height of each piston, you're looking for as little as .5mm difference in height which indicates a bend rod or crank.

    Hopefully its just a case of excess oil getting past the ringswhile it was running on its side then carboning up and sticking the combustion ring and not something more serious. IF its configured the way most industrial kobotas are for mobile plant is should have a low oil pressure cut out on it which hopefully means that once the oil pickup was exposed the engine shut itself down, If it doesnt have this feature its worth looking at putting it on.

    IF you have one piston thats showing higher than the other 2 when you do the hight check through the glow/injector hole thats a dead giveaway of a build up of crap on top of the piston. Theres a way of getting that out without having to strip the engine and it sounds like "subaru throttlebody cleaner" or the butchers method of "water/metho spray down the intake at high RPMS with the air cleaner off mate"
    Dave

    "In a Landrover the other vehicle is your crumple zone."

    For spelling call Rogets, for mechanicing call me.

    Fozzy, 2.25D SIII Ex DCA Ute
    Tdi autoManual d1 (gave it to the Mupion)
    Archaeoptersix 1990 6x6 dual cab(This things staying)


    If you've benefited from one or more of my posts please remember, your taxes paid for my skill sets, I'm just trying to make sure you get your monies worth.
    If you think you're in front on the deal, pay it forwards.

  6. #6
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    "the butchers method of water/metho spray down the intake at high RPMS with the air cleaner off mate"

    can I buy ringside seats to this?






    Keep us in the loop Albert
    "How long since you've visited The Good Oil?"

    '93 V8 Rossi
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    '21 to Infinity and Beyond!


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  7. #7
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    "can I buy ringside seats to this?"

    Ringside? I will be behind something solid with fingers in ears while the owner squirts away

  8. #8
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    guys, think hairdressers spray bottle, not fire hose....

    you're basically steam cleaning the top end of the engine.
    Dave

    "In a Landrover the other vehicle is your crumple zone."

    For spelling call Rogets, for mechanicing call me.

    Fozzy, 2.25D SIII Ex DCA Ute
    Tdi autoManual d1 (gave it to the Mupion)
    Archaeoptersix 1990 6x6 dual cab(This things staying)


    If you've benefited from one or more of my posts please remember, your taxes paid for my skill sets, I'm just trying to make sure you get your monies worth.
    If you think you're in front on the deal, pay it forwards.

  9. #9
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    Quote Originally Posted by Pedro_The_Swift View Post
    "the butchers method of water/metho spray down the intake at high RPMS with the air cleaner off mate"

    can I buy ringside seats to this?


    Keep us in the loop Albert
    It sounds like a Saturday night of fun and a Sunday emergency visit.

    How much are these tickets.

  10. #10
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    [QUOTE=Blknight.aus;2573649]

    "if its the rings your first step is a lightly loaded high speed run of the engine with an oil with a good detergent package or add some DEX III shock loading the thing may also help free up the rings."

    Im actually ok with the water spray, but could you expand on this any?
    Any brand oil you could recommend or are talking about a additive? And the other bit, how much Dex to add(per litre)
    If it is rings, it will save lot of work and leave more time to celebrate

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