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Kubota 3 Cylinder smoking Bent Rod

Discussion in 'General Industry Questions' started by Midnightmoon, Jan 27, 2017.

  1. Nige

    Nige Senior Member

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    I have absolutely zero experience on Kubota engines but I can tell you that "cylinder wash" caused by a leaking injector (it doesn't matter whether it's leaking from the tip or somewhere else, all that has to happen is that the fuel lands into the cylinder) has landed me in a world of hurt on various occasions in the past.
    Personally I cannot see how the injector got to leaking from the body (as you said it does when apply 120psi of air pressure to it) unless it had some type of internal defect.
    I could see ether wreaking all sorts of havoc inside an engine if over-used but IMHO the damage would be first seen on pistons, liners, and (possibly) cylinder head/valves. I'm not sure of any mechanism that could cause an injector to crack on the body by over-use of ether, especially if that injector body was not directly exposed to the compression/firing pressures in the cylinder. Where exactly is the "seam" where you located the crack, exposed inside the combustion chamber or above it in the cylinder head injector bore..?
     
    check likes this.
  2. Birken Vogt

    Birken Vogt Charter Member

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    Perhaps, but in what condition will the machine be when the engine is worn out with 25,000 hours? Most machines that these tiny engines go into are not D8s. The machine will not likely be rebuilt at that point so why make the motor to be inframed? It should be smaller and cheaper to make it parent bore. Better but more expensive is not always a winner for the owner's pocketbook.
     
  3. check

    check Senior Member

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    Your argument is akin to the argument in favor of disposable lighters and does have some merit, but if all manufacturers do this we soon become slaves to them and the bankers who finance these machines. The option to recondition machines and gently stretch their lifespan 30% is neither in the interests of manufacturers nor bankers, but often is in the interests of those who purchase them.
    Often the reason to re-sleeve an engine is that the cylinder is worn due to neglect, misuse, ether, contamination, lack of oil changes etc. so they may be getting rebuilt at anywhere from 3000 to 12000 hours. Granted, a parent bore 3 cylinder Kubota may be $150 cheaper, 3/4" shorter than it's sleeved counterpart and 15 pounds lighter, but the weight and size saving probably don't serve the owners interests in the long term, as his choices are so limited in cases like this. $5K for a new engine or buy a new tractor.
     
  4. Midnightmoon

    Midnightmoon Member

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    Right where the tip meets the threaded area below the threads[​IMG]
     
  5. Delmer

    Delmer Senior Member

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    You can easily rebuild the engine if anybody wants to. There are plenty of Amish in NY, are any of them of the Kubota sect around there? I know the shop here would fix it up and give that broken engine a new strict German home.

    I think it's a stretch to call a parent bore engine like this a design flaw. "Throwaway" sure, but you're throwing it away because it's lived out it's normal life or somebody screwed up bad. A three cylinder Kubota is almost competing against Briggs and Stratton more than modern sleeved diesel engines that size. Just look at all the medium duty diesel engines out there, Cummins B, Cat 3208, 3116, IH 6.9/7.3, Detroit 8.2. The only competitor in that size in truck engines that's sleeved would be the DT466, or Isuzu or Fuso. What percentage of DT466's in trucks do you think ever get rebuilt? Probably a small fraction of them, so the rest were needlessly expensive and heavy compared to a parent bore engine.

    I was thinking the 1995 kubota switch was from IDI to DI, but a little reading makes it seem like they might have switched back to IDI for some small diesels at that point, after making a push for DI in their small engines. And it led right back here to this thread

    https://www.heavyequipmentforums.com/threads/indirect-vs-direct-injection-small-diesels.59563/
     
  6. Welder Dave

    Welder Dave Senior Member

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    Kubota may have gone back to some IDI engines. My knowledge was more with the engines used in skid steers. Nothing wrong with a parent block engine. Ford tractors and industrial equipment used parent block engines. Ford used to claim that if an engine required a complete overhaul a parent bore was cheaper than a sleeved bore. When talking about an in frame rebuild doesn't that generally apply to large engines like in trucks? If you look after an engine and get 15-20,000 hours and have to pull it out and tear it down completely, wouldn't you want to do the same thing even it was sleeved engine?
     
  7. check

    check Senior Member

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    I don't know about today, but when I was in it 35 years ago, a Cummins truck engine would go 300,000 miles before it needed an in frame overhaul. At 600,000 miles it needed another in frame overhaul. If you wanted to get more than 900,000 miles out of it, you would have to remove the engine and tear it down completely, which was generally cost-prohibitive to do on a 900,000 mile truck.
    My 1955 Ford tractor came from the factory with sleeves, and that's a gas tractor. Ford sleeved all their industrial engines up to a certain date, then they figured it was cheaper to sell parent bore blocks and new tractors when those wore out.
    If you look after an engine and get 15 to 20K hours out of it, the unit it's in is not likely to last another 15K hours so you don't want to gamble the expense of a strip down overhaul. You want to do a "light overhaul" consisting of rolling in a set of rod and main bearings, restore compression and have the valves ground, the objective being to get another 3 to 5K hours out of it, which is a much better option than going to the dealer and the banker to get a new throw away machine.
     
  8. Birken Vogt

    Birken Vogt Charter Member

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    You mean here?

    1903-3020__17214.1474513706.jpg
     
  9. Delmer

    Delmer Senior Member

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    The story I always heard was "we farmed the whole 160 acres with one 8N, dad would plow all day and the boys would take shifts overnight, rebuilt that tractor every year" That was the technology of the day and it worked until something better came along.
     
  10. Midnightmoon

    Midnightmoon Member

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    Yes thats the spot on the injector
     
  11. Birken Vogt

    Birken Vogt Charter Member

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    So I guess it is possible it filled the hole up with diesel when off at some point.
     
  12. Midnightmoon

    Midnightmoon Member

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    Well kubota warranty came through. Best part was drilling the hole through the block into the cylinder.

    Cheaper to throw it away then send it back to kubota to be remanned. What a waste. We have a nice inventory of new parts now.
     
  13. kshansen

    kshansen Senior Member

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    Can you run a tap in the hole and put a pipe plug in it????
     
  14. Midnightmoon

    Midnightmoon Member

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    Anything is possible but it goes through the outside of block, through the water jacket and through the cylinder wall. It could be done but.........I'm not that into recycling. I will however save everything but the block for when another one out of warranty fails
     
  15. Birken Vogt

    Birken Vogt Charter Member

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    That might be a long time. They don't fail very often for my customers. Maybe your customers break them more often.

    But I would give serious thought to sleeving and plugging this one if you have the means to do it cheaply.
     
  16. ChiffChiff

    ChiffChiff Member

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    I have seen bent rods on 3 cylinder Kubotas used in Bobcat MT-52 and MT-55s when I worked at a dealer that were caused in a similar way. They would run them on a steep side hill and oil in the valve cover would pool up on the right side where that tube going to the intake manifold was. Oil would get sucked into the intake and hydrolock the engine and bend a rod.