BH90 dipper stick piston bent or broken

[enumclaw]

Hello, I just bent the dipper stick piston for the third time today while doing light duty work, scraping at the dirt on a pulled stump. This is the third time that the piston has been damaged or broken. The first time was under warranty. I don't know how it was bent but one day I noticed that it had a bow in it about 12" from the top pin. I used it anyway and the piston then broke. It was replaced at no charge. Six month later, when I next used it, the piston broke again after digging a 50' trench 3' deep. It was now out of warranty but the dealer replaced it anyway. The third time was today. I talked to the dealer who called Kubota and then called me back. He said that Kubota would pay for the cylinder but that I needed to pay for pickup/delivery and labor. They were going to install the new cylinder then adjust the mechanical stop as necessary such that when the piston was completely extended that it would not hit the stop. Not sure what the stop does in that case? I saw in previous posts a year or so ago that this problem had occurred with other BH90s and BH75s. If I had had the slightest idea that breaking pistons would be a recurring problem, I would have exercised it vigorously after the first time.

LS4330 HST
BH90

 

[jimainiac]

Boy, that's a shame about your backhoe. Sure sounds like something was mis-adjusted, and if they fixed it before, I'm surprised it keeps happening. It makes me glad I chose the Woods BH9000 when we got our L3830. I've horsed it around pretty hard digging out maple tree stumps, with no ill effects. Hope they get it right this time, sorry you're on the hook for the labor - doesn't seem like you should be.

 

[5030tinkerer]

I have been very. very pleased with my BH90. I have used it quite extensively, and have just installed Kubota's 36" bucket on it. I am very sorry to hear of the problems you've had - it sure sounds like something is adjusted improperly. I've maxed out the hydraulic capacity of my unit many, many times with no ill effects.

 

[Bob53]

I'm on number two for the dipper cylinder and not one year old yet on BH75. The 1st one rod cracked in half, they warrantied only because the replacement was a bigger cylinder. last month I bent the rod digging a stump out.
$720 to get it fixed, they said I was expecting too much from hoe and was not using it properly mostlikely. I asked them to check the relief valve, but do not get answer. i really did not think pushing it, but then again this is my 1st hoe. I'm keeping the bill and going to check end summer or next year if they had to upgrade cylinder again, if they do , going to try and get money back. I've read threads on this problem and my ground is rocky and not much easy digging so I may have purchased to small a hoe for what i want to do. I never go down more than 3 foot but ???

 

[JerryG]

Over the last 6 -7 years there have been several that have this happen to. ALL of them without exception have bent when digging, scraping under power or prying very close to the backhoe frame. The closer the bucket is to the BH frame the higher the chance of mangling that cylinder. Kubota increased the rod diameter for one of their BHs trying to fix the problem. That will decrease the chance of damage, but will not eliminate it. Also the larger the rod diameter the less power the cylinder will have, so it actually helps in two ways. I have seen this happen to at least 4 different brands of compact BHs. It isn't limited to one brand.

 

[Bob53]

Yes as with anything if you try hard enough you can break it no matter how well designed. The dealer was nice enough to come out and see what I was doing when the cylinder went the the other week. He said more or less what you said , watch it when the rod is extended far out of the cylinder.
All I'm saying is its great to have fourms like this so if other are having same problem you can either change you're ways or find out it might be a weak link on a certain model. I know its gray to a certain point, just if someday kubota feels it warrants a larger cylinder because of failures, hopefully that they will take care of people that had earlier failures. In the end it biols down too how many failures they are getting on models befrore they look into it real close.

 

[enumclaw]

Jim, Thanks for you comments. I did look at several Woods models before I bought the BH90 but I'm not sure that I tried the BH9000. This is my first (and I expected it to be my last) hoe. If I give up on the BH90 I will definitely check out the Woods products with a more experienced eye.

 

[enumclaw]

Thanks for the good news 5030tinkerer!! There is hope for my BH90 yet. I chose the BH90 over the BH75 or other manufacturer's backhoes because it appeared to be constructed of extremely heavy duty steel with a lot of attention to detail. Hoses were enclosed or routed to be protected. Grease fittings on all bearings. Extra plates welded around pivot points. Massive mounting plates bolted to the frame. Very impressive workmanship. The first time that the dipper stick piston bent, I had been working at dusk under trees and when I discovered that it was bent, I thought that perhaps I had run into a low hanging branch somehow and so the damage was my fault. I continued to use it and then it snapped. The second time, I had been digging about 50' of a three foot deep ditch in fairly soft dirt and rocks in the middle of a field in the afternoon when, bang! It snapped. Anyway, I chose the 12" bucket because in general my ground has a lot of rocks and clay and I felt that the smaller bucket could exert more digging force. I don't know what needs to be adjusted. I don't see any mechanical stop. I'm glad that you have had good service and I hope that the dealer can fix mine to the same standards. In my case, clearly the hydraulic capacity exceeds the mechanical capacity which makes me think that the piston is too long and not rigid enough, ie a desing flaw.

 

[enumclaw]

Thanks for your story Bob53. I'm sorry to hear that you are having the same problem. It seems to me that the dealer's argument that you are "expecting too much of your backhoe" is a cop out. It's true that you should use the right tool for the job but if you use too small a tool, if the tool is well made, it should just take longer, as when you use a 4' mower instead of a 6' mower, or fail to do the job as when you try to pick up an immovable object with your loader. The mower or loader should not break. That the piston did break indicates a design flaw that allows too much pressure or too much extension of the piston or a weak piston. Furthermore, there was no indication that failure was imminent , no squealing or engine stalling so how can one know when one is approaching the operational limit? I bought the heavy duty model, the BH90, because I thought that it exceeded my requirements and hence that I would never even exceed it's capacity but I didn't think that I needed a Case 580K Construction King to dig some ditches and mess with stumps.

 

[enumclaw]

Thanks for the background JerryG. It is interesting that breaking dipper stick cylinders is not only Kubota's problem but be that as it may, I paid more for Kubota quality and I expect it to fail gracefully or at least give me an indication that I am approaching a limit. It should not fail catastrophically. If digging close to the frame is a problem, then a sensor should reduce pressure in that geometry or at the very least a whistle should blow to indicate that the hoe is under stress and that I should ease up. To have it just break with no warning is unacceptable.