BH75 Piston broke, twice! Design problem??

BX2230Dude · May 2, 2005

After reading several posts about bent cylinders on the BH75 and BH90 and comments that the user was digging too close to the tractor, or using the wrong digging angle on the bucket, etc., I thought I would post a link to a book I found helpful when learning how to operate a TLB. I read an earlier edition of the book and it was full of useful information, photos, diagrams, etc. Should be required reading for TLB owners.

TLB Book

KLS59 · May 2, 2005

Recently bent the bucket piston/cylinder on my BH90, which is attached to an L5030. Gave good service for a few months, then bent when digging a stump. Was it me or was it a poor design? How can I get a replacement, and where? I've read it's possible to replace this part with non-Kubota parts? If so, who can I contact? And, by the way, I need this thing like yesterday... Thanks for any info.

Junkman · May 3, 2005

You might start by filling out your bio. Without knowing what part of the country you are located in, the best that I can do is suggest that you look in the yellow pages for hydraulic dealers and start calling to see who sells what. Take the old cylinder to the dealer that you select and they can either repair or make you a new cylinder. It isn't going to be cheap, but that is the cost of owning machinery. If the tractor is less than 1 year old, contact your selling dealer about a warranty claim. With the rash of bent/broken pistons, you never know how they will deal with this one. Chances are, if you have problems, mention that you know of others that have also have had bent pistons, and you were wondering if there is a manufacturing defect in the product. Can't hurt to ask... /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif

kubotabilly · May 3, 2005

Junkman,
I was at my dealer yesterday and a gentleman pulls in with a Kubota 4690 backhoe for repair. The repair was a bent cylinder. The same cylinder that the others have been bending. I asked him what had happened and he said, "same thing as before". I said WHAT /forums/images/graemlins/confused.gif. "Yea, this is the third cylinder that I bent and Kubota wanted me to bring the hoe in for some testing". To make a long story short, the problem was in the relief valve to that cylinder. One side of the valve was popping off at the recommended 2300-2400 psi and the other side was not popping off until over 5000 psi /forums/images/graemlins/shocked.gif. The cylinder was not made for that kind of pressure and as a result, bends. It seems to be a design error or a assembly line error, no one really said, but Kubota is footing the bill. I thought this info may help anyone else with this problem.

Bill

MacPDaddy · Jul 13, 2009

Here are some pictures of a BH75 that ran flawlessly through Saturday.
It was purchased December 2005, I am attempting to have Kubota replace the cylinder based on your information.
I appreciate everyone posting on this.

bigballer · Jul 14, 2009

hi mac- what size is your cylinder? should be a stamp on the outside of it. i have an '07 BH-75 with a 32mm cylinder and haven't had that issue. i've dug alot with it (over 100 stumps and close to 1000' of trenching).. best of luck to you, let us know how kubota handles this. by the way, what is the cost of a replacement cylinder?

MessickFarmEqu · Jul 14, 2009

the rest of this thread was from 2005. That shows how wide spread of a problem this is. If you ask nicely you can probably get Kubota to chip it and cover some of your parts, or throw that larger cylinder on there.

rdsaustintx · Jul 14, 2009

MacP,

Man those photos are impressive (and scary). Amazing it took so long to fail. Judging from the dates on the thread it was a frequent problem, but got resolved years ago.

When Messick posts, smart owners listen. The dealers that participate here are great guys.

Russell in Texas

Sparkyca · Jul 15, 2009

Been around backhoes a long time, and one thing that seems common on bent cylinders is 'Stumps'. If you hook the hoe over a stump and then pull forward with a 4wd tractor there is no relief built into the system and the pressure you will generate with the tractive effort is in the 10's of thousands of PSI. I guarantee something will bend.

rdsaustintx · Jul 15, 2009

Sparkyca said:
Been around backhoes a long time, and one thing that seems common on bent cylinders is 'Stumps'. If you hook the hoe over a stump and then pull forward with a 4wd tractor there is no relief built into the system and the pressure you will generate with the tractive effort is in the 10's of thousands of PSI. I guarantee something will bend.

Ahhh. I understand that. Similar to when you hit a vertical object with an FEL bucket in dump position. Mechanical advantage at the cylinder is huge.

But curling under a stump too close to the tractor? This pretty much describes how I chew through roots or limestone. Get in close, get teeth under a ledge and use the curl force (and leverage) to force a break. Dipper and curl cylinders are at relief and it pulls straight down on the tractor. So hard you can see the frame flex. Thought that was the right way to do it?

The operator books sounds great, but I don't have time to order and read it.